diff --git a/crates/fj-kernel/src/algorithms/transform.rs b/crates/fj-kernel/src/algorithms/transform.rs
index 233b2e429..11e11683f 100644
--- a/crates/fj-kernel/src/algorithms/transform.rs
+++ b/crates/fj-kernel/src/algorithms/transform.rs
@@ -3,8 +3,8 @@
 use fj_math::{Transform, Vector};
 
 use crate::objects::{
-    Curve, Cycle, Edge, Face, GlobalCurve, GlobalVertex, Shell, Sketch, Solid,
-    Surface, SurfaceVertex, Vertex,
+    Curve, Cycle, Edge, Face, Faces, GlobalCurve, GlobalVertex, Shell, Sketch,
+    Solid, Surface, SurfaceVertex, Vertex,
 };
 
 /// Transform an object
@@ -90,6 +90,14 @@ impl TransformObject for Face {
     }
 }
 
+impl TransformObject for Faces {
+    fn transform(self, transform: &Transform) -> Self {
+        let mut faces = Faces::new();
+        faces.extend(self.into_iter().map(|face| face.transform(transform)));
+        faces
+    }
+}
+
 impl TransformObject for GlobalCurve {
     fn transform(self, transform: &Transform) -> Self {
         let kind = self.kind().transform(transform);
@@ -162,13 +170,6 @@ impl TransformObject for Vertex {
     }
 }
 
-/// Transform a shape
-pub fn transform_faces(faces: &mut Vec<Face>, transform: &Transform) {
-    for face in faces {
-        *face = face.clone().transform(transform);
-    }
-}
-
 fn transform_cycles<'a>(
     cycles: impl IntoIterator<Item = &'a Cycle> + 'a,
     transform: &'a Transform,
diff --git a/crates/fj-operations/src/group.rs b/crates/fj-operations/src/group.rs
index 03e465533..b4c441855 100644
--- a/crates/fj-operations/src/group.rs
+++ b/crates/fj-operations/src/group.rs
@@ -4,14 +4,14 @@ use fj_kernel::{
         approx::Tolerance,
         validate::{Validate, Validated, ValidationConfig, ValidationError},
     },
-    objects::Face,
+    objects::Faces,
 };
 use fj_math::Aabb;
 
 use super::Shape;
 
 impl Shape for fj::Group {
-    type Brep = Vec<Face>;
+    type Brep = Faces;
 
     fn compute_brep(
         &self,
@@ -19,7 +19,7 @@ impl Shape for fj::Group {
         tolerance: Tolerance,
         debug_info: &mut DebugInfo,
     ) -> Result<Validated<Self::Brep>, ValidationError> {
-        let mut faces = Vec::new();
+        let mut faces = Faces::new();
 
         let a = self.a.compute_brep(config, tolerance, debug_info)?;
         let b = self.b.compute_brep(config, tolerance, debug_info)?;
diff --git a/crates/fj-operations/src/lib.rs b/crates/fj-operations/src/lib.rs
index 7fcbff25a..8e1783d5b 100644
--- a/crates/fj-operations/src/lib.rs
+++ b/crates/fj-operations/src/lib.rs
@@ -30,7 +30,7 @@ use fj_kernel::{
         approx::Tolerance,
         validate::{Validate, Validated, ValidationConfig, ValidationError},
     },
-    objects::{Face, Sketch},
+    objects::{Faces, Sketch},
 };
 use fj_math::Aabb;
 
@@ -55,7 +55,7 @@ pub trait Shape {
 }
 
 impl Shape for fj::Shape {
-    type Brep = Vec<Face>;
+    type Brep = Faces;
 
     fn compute_brep(
         &self,
@@ -68,8 +68,6 @@ impl Shape for fj::Shape {
                 .compute_brep(config, tolerance, debug_info)?
                 .into_inner()
                 .into_faces()
-                .into_iter()
-                .collect::<Vec<_>>()
                 .validate_with_config(config),
             Self::Group(shape) => {
                 shape.compute_brep(config, tolerance, debug_info)
@@ -78,8 +76,12 @@ impl Shape for fj::Shape {
                 .compute_brep(config, tolerance, debug_info)?
                 .into_inner()
                 .into_shells()
-                .flat_map(|shell| shell.into_faces())
-                .collect::<Vec<_>>()
+                .map(|shell| shell.into_faces())
+                .reduce(|mut a, b| {
+                    a.extend(b);
+                    a
+                })
+                .unwrap_or_default()
                 .validate_with_config(config),
             Self::Transform(shape) => {
                 shape.compute_brep(config, tolerance, debug_info)
diff --git a/crates/fj-operations/src/transform.rs b/crates/fj-operations/src/transform.rs
index c3a118572..8175c1d0d 100644
--- a/crates/fj-operations/src/transform.rs
+++ b/crates/fj-operations/src/transform.rs
@@ -2,17 +2,17 @@ use fj_interop::debug::DebugInfo;
 use fj_kernel::{
     algorithms::{
         approx::Tolerance,
-        transform::transform_faces,
+        transform::TransformObject,
         validate::{Validate, Validated, ValidationConfig, ValidationError},
     },
-    objects::Face,
+    objects::Faces,
 };
 use fj_math::{Aabb, Transform, Vector};
 
 use super::Shape;
 
 impl Shape for fj::Transform {
-    type Brep = Vec<Face>;
+    type Brep = Faces;
 
     fn compute_brep(
         &self,
@@ -20,12 +20,11 @@ impl Shape for fj::Transform {
         tolerance: Tolerance,
         debug_info: &mut DebugInfo,
     ) -> Result<Validated<Self::Brep>, ValidationError> {
-        let mut faces = self
+        let faces = self
             .shape
             .compute_brep(config, tolerance, debug_info)?
-            .into_inner();
-
-        transform_faces(&mut faces, &make_transform(self));
+            .into_inner()
+            .transform(&make_transform(self));
 
         faces.validate_with_config(config)
     }