diff --git a/src/abs_diff_eq.rs b/src/abs_diff_eq.rs
index cf13ec3..67f59c7 100644
--- a/src/abs_diff_eq.rs
+++ b/src/abs_diff_eq.rs
@@ -5,7 +5,10 @@ use num_traits::float::FloatCore;
 use std::{cell, f32, f64};
 
 /// Equality that is defined using the absolute difference of two numbers.
-pub trait AbsDiffEq: PartialEq {
+pub trait AbsDiffEq<Rhs = Self>: PartialEq<Rhs>
+where
+    Rhs: ?Sized,
+{
     /// Used for specifying relative comparisons.
     type Epsilon;
 
@@ -17,10 +20,10 @@ pub trait AbsDiffEq: PartialEq {
 
     /// A test for equality that uses the absolute difference to compute the approximate
     /// equality of two numbers.
-    fn abs_diff_eq(&self, other: &Self, epsilon: Self::Epsilon) -> bool;
+    fn abs_diff_eq(&self, other: &Rhs, epsilon: Self::Epsilon) -> bool;
 
     /// The inverse of `ApproxEq::abs_diff_eq`.
-    fn abs_diff_ne(&self, other: &Self, epsilon: Self::Epsilon) -> bool {
+    fn abs_diff_ne(&self, other: &Rhs, epsilon: Self::Epsilon) -> bool {
         !Self::abs_diff_eq(self, other, epsilon)
     }
 }
@@ -143,21 +146,22 @@ impl<T: AbsDiffEq + ?Sized> AbsDiffEq for cell::RefCell<T> {
     }
 }
 
-impl<T: AbsDiffEq> AbsDiffEq for [T]
+impl<A, B> AbsDiffEq<[B]> for [A]
 where
-    T::Epsilon: Clone,
+    A: AbsDiffEq<B>,
+    A::Epsilon: Clone,
 {
-    type Epsilon = T::Epsilon;
+    type Epsilon = A::Epsilon;
 
     #[inline]
-    fn default_epsilon() -> T::Epsilon {
-        T::default_epsilon()
+    fn default_epsilon() -> A::Epsilon {
+        A::default_epsilon()
     }
 
     #[inline]
-    fn abs_diff_eq(&self, other: &[T], epsilon: T::Epsilon) -> bool {
+    fn abs_diff_eq(&self, other: &[B], epsilon: A::Epsilon) -> bool {
         self.len() == other.len()
-            && Iterator::zip(self.iter(), other).all(|(x, y)| T::abs_diff_eq(x, y, epsilon.clone()))
+            && Iterator::zip(self.iter(), other).all(|(x, y)| A::abs_diff_eq(x, y, epsilon.clone()))
     }
 }
 
diff --git a/src/lib.rs b/src/lib.rs
index 6e45373..a857f47 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -188,40 +188,49 @@ pub use ulps_eq::UlpsEq;
 /// AbsDiff::default().eq(&1.0, &1.0);
 /// AbsDiff::default().epsilon(f64::EPSILON).eq(&1.0, &1.0);
 /// ```
-pub struct AbsDiff<T: AbsDiffEq + ?Sized> {
+pub struct AbsDiff<A, B = A>
+where
+    A: AbsDiffEq<B> + ?Sized,
+    B: ?Sized,
+{
     /// The tolerance to use when testing values that are close together.
-    pub epsilon: T::Epsilon,
+    pub epsilon: A::Epsilon,
 }
 
-impl<T: AbsDiffEq + ?Sized> Default for AbsDiff<T> {
+impl<A, B> Default for AbsDiff<A, B>
+where
+    A: AbsDiffEq<B> + ?Sized,
+    B: ?Sized,
+{
     #[inline]
-    fn default() -> AbsDiff<T> {
+    fn default() -> AbsDiff<A, B> {
         AbsDiff {
-            epsilon: T::default_epsilon(),
+            epsilon: A::default_epsilon(),
         }
     }
 }
 
-impl<T> AbsDiff<T>
+impl<A, B> AbsDiff<A, B>
 where
-    T: AbsDiffEq + ?Sized,
+    A: AbsDiffEq<B> + ?Sized,
+    B: ?Sized,
 {
     /// Replace the epsilon value with the one specified.
     #[inline]
-    pub fn epsilon(self, epsilon: T::Epsilon) -> AbsDiff<T> {
+    pub fn epsilon(self, epsilon: A::Epsilon) -> AbsDiff<A, B> {
         AbsDiff { epsilon, ..self }
     }
 
     /// Peform the equality comparison
     #[inline]
-    pub fn eq(self, lhs: &T, rhs: &T) -> bool {
-        T::abs_diff_eq(lhs, rhs, self.epsilon)
+    pub fn eq(self, lhs: &A, rhs: &B) -> bool {
+        A::abs_diff_eq(lhs, rhs, self.epsilon)
     }
 
     /// Peform the inequality comparison
     #[inline]
-    pub fn ne(self, lhs: &T, rhs: &T) -> bool {
-        T::abs_diff_ne(lhs, rhs, self.epsilon)
+    pub fn ne(self, lhs: &A, rhs: &B) -> bool {
+        A::abs_diff_ne(lhs, rhs, self.epsilon)
     }
 }
 
@@ -243,33 +252,45 @@ where
 /// Relative::default().epsilon(f64::EPSILON).max_relative(1.0).eq(&1.0, &1.0);
 /// Relative::default().max_relative(1.0).epsilon(f64::EPSILON).eq(&1.0, &1.0);
 /// ```
-pub struct Relative<T: RelativeEq + ?Sized> {
+pub struct Relative<A, B = A>
+where
+    A: RelativeEq<B> + ?Sized,
+    B: ?Sized,
+{
     /// The tolerance to use when testing values that are close together.
-    pub epsilon: T::Epsilon,
+    pub epsilon: A::Epsilon,
     /// The relative tolerance for testing values that are far-apart.
-    pub max_relative: T::Epsilon,
+    pub max_relative: A::Epsilon,
 }
 
-impl<T: RelativeEq + ?Sized> Default for Relative<T> {
+impl<A, B> Default for Relative<A, B>
+where
+    A: RelativeEq<B> + ?Sized,
+    B: ?Sized,
+{
     #[inline]
-    fn default() -> Relative<T> {
+    fn default() -> Relative<A, B> {
         Relative {
-            epsilon: T::default_epsilon(),
-            max_relative: T::default_max_relative(),
+            epsilon: A::default_epsilon(),
+            max_relative: A::default_max_relative(),
         }
     }
 }
 
-impl<T: RelativeEq + ?Sized> Relative<T> {
+impl<A, B> Relative<A, B>
+where
+    A: RelativeEq<B> + ?Sized,
+    B: ?Sized,
+{
     /// Replace the epsilon value with the one specified.
     #[inline]
-    pub fn epsilon(self, epsilon: T::Epsilon) -> Relative<T> {
+    pub fn epsilon(self, epsilon: A::Epsilon) -> Relative<A, B> {
         Relative { epsilon, ..self }
     }
 
     /// Replace the maximum relative value with the one specified.
     #[inline]
-    pub fn max_relative(self, max_relative: T::Epsilon) -> Relative<T> {
+    pub fn max_relative(self, max_relative: A::Epsilon) -> Relative<A, B> {
         Relative {
             max_relative,
             ..self
@@ -278,14 +299,14 @@ impl<T: RelativeEq + ?Sized> Relative<T> {
 
     /// Peform the equality comparison
     #[inline]
-    pub fn eq(self, lhs: &T, rhs: &T) -> bool {
-        T::relative_eq(lhs, rhs, self.epsilon, self.max_relative)
+    pub fn eq(self, lhs: &A, rhs: &B) -> bool {
+        A::relative_eq(lhs, rhs, self.epsilon, self.max_relative)
     }
 
     /// Peform the inequality comparison
     #[inline]
-    pub fn ne(self, lhs: &T, rhs: &T) -> bool {
-        T::relative_ne(lhs, rhs, self.epsilon, self.max_relative)
+    pub fn ne(self, lhs: &A, rhs: &B) -> bool {
+        A::relative_ne(lhs, rhs, self.epsilon, self.max_relative)
     }
 }
 
@@ -307,48 +328,57 @@ impl<T: RelativeEq + ?Sized> Relative<T> {
 /// Ulps::default().epsilon(f64::EPSILON).max_ulps(4).eq(&1.0, &1.0);
 /// Ulps::default().max_ulps(4).epsilon(f64::EPSILON).eq(&1.0, &1.0);
 /// ```
-pub struct Ulps<T: UlpsEq + ?Sized> {
+pub struct Ulps<A, B = A>
+where
+    A: UlpsEq<B> + ?Sized,
+    B: ?Sized,
+{
     /// The tolerance to use when testing values that are close together.
-    pub epsilon: T::Epsilon,
+    pub epsilon: A::Epsilon,
     /// The ULPs to tolerate when testing values that are far-apart.
     pub max_ulps: u32,
 }
 
-impl<T: UlpsEq + ?Sized> Default for Ulps<T>
+impl<A, B> Default for Ulps<A, B>
 where
-    T: UlpsEq,
+    A: UlpsEq<B> + ?Sized,
+    B: ?Sized,
 {
     #[inline]
-    fn default() -> Ulps<T> {
+    fn default() -> Ulps<A, B> {
         Ulps {
-            epsilon: T::default_epsilon(),
-            max_ulps: T::default_max_ulps(),
+            epsilon: A::default_epsilon(),
+            max_ulps: A::default_max_ulps(),
         }
     }
 }
 
-impl<T: UlpsEq + ?Sized> Ulps<T> {
+impl<A, B> Ulps<A, B>
+where
+    A: UlpsEq<B> + ?Sized,
+    B: ?Sized,
+{
     /// Replace the epsilon value with the one specified.
     #[inline]
-    pub fn epsilon(self, epsilon: T::Epsilon) -> Ulps<T> {
+    pub fn epsilon(self, epsilon: A::Epsilon) -> Ulps<A, B> {
         Ulps { epsilon, ..self }
     }
 
     /// Replace the max ulps value with the one specified.
     #[inline]
-    pub fn max_ulps(self, max_ulps: u32) -> Ulps<T> {
+    pub fn max_ulps(self, max_ulps: u32) -> Ulps<A, B> {
         Ulps { max_ulps, ..self }
     }
 
     /// Peform the equality comparison
     #[inline]
-    pub fn eq(self, lhs: &T, rhs: &T) -> bool {
-        T::ulps_eq(lhs, rhs, self.epsilon, self.max_ulps)
+    pub fn eq(self, lhs: &A, rhs: &B) -> bool {
+        A::ulps_eq(lhs, rhs, self.epsilon, self.max_ulps)
     }
 
     /// Peform the inequality comparison
     #[inline]
-    pub fn ne(self, lhs: &T, rhs: &T) -> bool {
-        T::ulps_ne(lhs, rhs, self.epsilon, self.max_ulps)
+    pub fn ne(self, lhs: &A, rhs: &B) -> bool {
+        A::ulps_ne(lhs, rhs, self.epsilon, self.max_ulps)
     }
 }
diff --git a/src/relative_eq.rs b/src/relative_eq.rs
index 52c1333..5498825 100644
--- a/src/relative_eq.rs
+++ b/src/relative_eq.rs
@@ -8,7 +8,10 @@ use AbsDiffEq;
 
 /// Equality comparisons between two numbers using both the absolute difference and
 /// relative based comparisons.
-pub trait RelativeEq: AbsDiffEq {
+pub trait RelativeEq<Rhs = Self>: AbsDiffEq<Rhs>
+where
+    Rhs: ?Sized,
+{
     /// The default relative tolerance for testing values that are far-apart.
     ///
     /// This is used when no `max_relative` value is supplied to the `relative_eq` macro.
@@ -17,7 +20,7 @@ pub trait RelativeEq: AbsDiffEq {
     /// A test for equality that uses a relative comparison if the values are far apart.
     fn relative_eq(
         &self,
-        other: &Self,
+        other: &Rhs,
         epsilon: Self::Epsilon,
         max_relative: Self::Epsilon,
     ) -> bool;
@@ -25,7 +28,7 @@ pub trait RelativeEq: AbsDiffEq {
     /// The inverse of `ApproxEq::relative_eq`.
     fn relative_ne(
         &self,
-        other: &Self,
+        other: &Rhs,
         epsilon: Self::Epsilon,
         max_relative: Self::Epsilon,
     ) -> bool {
@@ -152,20 +155,21 @@ impl<T: RelativeEq + ?Sized> RelativeEq for cell::RefCell<T> {
     }
 }
 
-impl<T: RelativeEq> RelativeEq for [T]
+impl<A, B> RelativeEq<[B]> for [A]
 where
-    T::Epsilon: Clone,
+    A: RelativeEq<B>,
+    A::Epsilon: Clone,
 {
     #[inline]
-    fn default_max_relative() -> T::Epsilon {
-        T::default_max_relative()
+    fn default_max_relative() -> A::Epsilon {
+        A::default_max_relative()
     }
 
     #[inline]
-    fn relative_eq(&self, other: &[T], epsilon: T::Epsilon, max_relative: T::Epsilon) -> bool {
+    fn relative_eq(&self, other: &[B], epsilon: A::Epsilon, max_relative: A::Epsilon) -> bool {
         self.len() == other.len()
             && Iterator::zip(self.iter(), other)
-                .all(|(x, y)| T::relative_eq(x, y, epsilon.clone(), max_relative.clone()))
+                .all(|(x, y)| A::relative_eq(x, y, epsilon.clone(), max_relative.clone()))
     }
 }
 
diff --git a/src/ulps_eq.rs b/src/ulps_eq.rs
index 132abff..b177aaa 100644
--- a/src/ulps_eq.rs
+++ b/src/ulps_eq.rs
@@ -8,17 +8,20 @@ use AbsDiffEq;
 
 /// Equality comparisons between two numbers using both the absolute difference and ULPs
 /// (Units in Last Place) based comparisons.
-pub trait UlpsEq: AbsDiffEq {
+pub trait UlpsEq<Rhs = Self>: AbsDiffEq<Rhs>
+where
+    Rhs: ?Sized,
+{
     /// The default ULPs to tolerate when testing values that are far-apart.
     ///
     /// This is used when no `max_ulps` value is supplied to the `ulps_eq` macro.
     fn default_max_ulps() -> u32;
 
     /// A test for equality that uses units in the last place (ULP) if the values are far apart.
-    fn ulps_eq(&self, other: &Self, epsilon: Self::Epsilon, max_ulps: u32) -> bool;
+    fn ulps_eq(&self, other: &Rhs, epsilon: Self::Epsilon, max_ulps: u32) -> bool;
 
     /// The inverse of `ApproxEq::ulps_eq`.
-    fn ulps_ne(&self, other: &Self, epsilon: Self::Epsilon, max_ulps: u32) -> bool {
+    fn ulps_ne(&self, other: &Rhs, epsilon: Self::Epsilon, max_ulps: u32) -> bool {
         !Self::ulps_eq(self, other, epsilon, max_ulps)
     }
 }
@@ -114,20 +117,21 @@ impl<T: UlpsEq + ?Sized> UlpsEq for cell::RefCell<T> {
     }
 }
 
-impl<T: UlpsEq> UlpsEq for [T]
+impl<A, B> UlpsEq<[B]> for [A]
 where
-    T::Epsilon: Clone,
+    A: UlpsEq<B>,
+    A::Epsilon: Clone,
 {
     #[inline]
     fn default_max_ulps() -> u32 {
-        T::default_max_ulps()
+        A::default_max_ulps()
     }
 
     #[inline]
-    fn ulps_eq(&self, other: &[T], epsilon: T::Epsilon, max_ulps: u32) -> bool {
+    fn ulps_eq(&self, other: &[B], epsilon: A::Epsilon, max_ulps: u32) -> bool {
         self.len() == other.len()
             && Iterator::zip(self.iter(), other)
-                .all(|(x, y)| T::ulps_eq(x, y, epsilon.clone(), max_ulps.clone()))
+                .all(|(x, y)| A::ulps_eq(x, y, epsilon.clone(), max_ulps.clone()))
     }
 }