diff --git a/crates/coremem/src/stim/vector_field.rs b/crates/coremem/src/stim/vector_field.rs
index 03e21d2..6b0aa70 100644
--- a/crates/coremem/src/stim/vector_field.rs
+++ b/crates/coremem/src/stim/vector_field.rs
@@ -1,6 +1,6 @@
 use crate::geom::{Coord as _, HasCrossSection, Index, Region};
 use crate::real::Real;
-use crate::stim::{Fields, Stimulus};
+use crate::stim::Fields;
 use coremem_cross::dim::DimSlice;
 use coremem_cross::vec::Vec3u;
 
@@ -29,45 +29,33 @@ where
     }
 }
 
-/// Apply a time-varying stimulus uniformly across some region
+/// restrict the VectorField to just the specified region, letting it be zero everywhere else
 #[derive(Clone)]
-pub struct RegionGated<G, S> {
+pub struct RegionGated<G, V> {
     region: G,
-    stim: S,
+    field: V,
 }
 
-impl<G, S> RegionGated<G, S> {
-    pub fn new(region: G, stim: S) -> Self {
+impl<G, V> RegionGated<G, V> {
+    pub fn new(region: G, field: V) -> Self {
         Self {
-            region, stim
+            region, field
         }
     }
 }
 
-// TODO: is this necessary?
-impl<R: Real, G: Region + Sync, S: Stimulus<R> + Sync> Stimulus<R> for RegionGated<G, S> {
-    fn at(&self, t_sec: R, feat_size: R, loc: Index) -> Fields<R> {
-        if self.region.contains(loc.to_meters(feat_size.cast())) {
-            self.stim.at(t_sec, feat_size, loc)
-        } else {
-            Fields::default()
-        }
-    }
-}
-
-impl<R: Real, G: Region + Sync, S: VectorField<R>> VectorField<R> for RegionGated<G, S> {
+impl<R: Real, G: Region + Sync, V: VectorField<R>> VectorField<R> for RegionGated<G, V> {
     fn at(&self, feat_size: R, loc: Index) -> Fields<R> {
         if self.region.contains(loc.to_meters(feat_size.cast())) {
-            self.stim.at(feat_size, loc)
+            self.field.at(feat_size, loc)
         } else {
             Fields::default()
         }
     }
 }
 
-/// apply a stimulus across some region.
-/// the stimulus seen at each point is based on its angle about the specified ray.
-/// the stimulus has equal E and H vectors. if you want just one, filter it one with `Scaled`.
+/// VectorField whose field at each point is based on its angle about the specified ray.
+/// the field has equal E and H vectors. if you want just one, filter it out with `Scaled`.
 #[derive(Clone)]
 pub struct CurlVectorField<G> {
     region: G,