diff --git a/src/hydro/Gadget2/hydro_iact.h b/src/hydro/Gadget2/hydro_iact.h
index c556683120f49f608db2dc1f3e2f6f47687b7bfb..47e0dd454db8b52be6eb2aa068ed65121e7884d2 100644
--- a/src/hydro/Gadget2/hydro_iact.h
+++ b/src/hydro/Gadget2/hydro_iact.h
@@ -403,7 +403,7 @@ runner_iact_nonsym_2_vec_density(float *R2, float *Dx, float *Dy, float *Dz, vec
   vector dvdr2;
   vector curlvrx2, curlvry2, curlvrz2;
 
-  /* Get the masses. */
+  /* Fill the vectors. */
   mj.v = vec_load(Mj);
   mj2.v = vec_load(&Mj[VEC_SIZE]);
   vjx.v = vec_load(Vjx);
@@ -430,6 +430,7 @@ runner_iact_nonsym_2_vec_density(float *R2, float *Dx, float *Dy, float *Dz, vec
   xi.v = vec_mul(r.v, hi_inv.v);
   xi2.v = vec_mul(r_2.v, hi_inv.v);
 
+  /* Calculate the kernel for two particles. */
   kernel_deval_2_vec(&xi, &wi, &wi_dx,&xi2, &wi2, &wi_dx2);
 
   /* Compute dv. */
diff --git a/src/kernel_hydro.h b/src/kernel_hydro.h
index a9f10ecdf2e6235ca7fa62c697dd502056a7a5ce..5a7965bb0ab889ad2654df603ab66dca9bb5f46f 100644
--- a/src/kernel_hydro.h
+++ b/src/kernel_hydro.h
@@ -363,6 +363,7 @@ __attribute__((always_inline)) INLINE static void kernel_deval_vec(
       dw_dx->v * kernel_constant_vec.v * kernel_gamma_inv_dim_plus_one_vec.v;
 }
 
+/* Define constant vectors for the Wendland C2 kernel coefficients. */
 #ifdef WENDLAND_C2_KERNEL
 static const vector c0 = FILL_VEC(4.f);
 static const vector c1 = FILL_VEC(-15.f);
@@ -373,7 +374,7 @@ static const vector c5 = FILL_VEC(1.f);
 #endif
 
 /**
- * @brief Computes the kernel function and its derivative using two interleaved vectors.
+ * @brief Computes the kernel function and its derivative for two particles using interleaved vectors.
  *
  * Return 0 if $u > \\gamma = H/h$
  *