diff --git a/halo2-base/src/gates/builder/mod.rs b/halo2-base/src/gates/builder/mod.rs
index 61adb301..ab2864ea 100644
--- a/halo2-base/src/gates/builder/mod.rs
+++ b/halo2-base/src/gates/builder/mod.rs
@@ -593,6 +593,24 @@ impl<F: ScalarField> GateCircuitBuilder<F> {
 pub struct RangeCircuitBuilder<F: ScalarField>(pub GateCircuitBuilder<F>);
 
 impl<F: ScalarField> RangeCircuitBuilder<F> {
+    /// Convenience function to create a new [RangeCircuitBuilder] with a given [CircuitBuilderStage].
+    pub fn from_stage(
+        stage: CircuitBuilderStage,
+        builder: GateThreadBuilder<F>,
+        config_params: BaseConfigParams,
+        break_points: Option<MultiPhaseThreadBreakPoints>,
+    ) -> Self {
+        match stage {
+            CircuitBuilderStage::Keygen => Self::keygen(builder, config_params),
+            CircuitBuilderStage::Mock => Self::mock(builder, config_params),
+            CircuitBuilderStage::Prover => Self::prover(
+                builder,
+                config_params,
+                break_points.expect("break points must be pre-calculated for prover"),
+            ),
+        }
+    }
+
     /// Creates an instance of the [RangeCircuitBuilder] and executes in keygen mode.
     pub fn keygen(builder: GateThreadBuilder<F>, config_params: BaseConfigParams) -> Self {
         Self(GateCircuitBuilder::keygen(builder, config_params))
@@ -678,6 +696,20 @@ pub struct RangeWithInstanceCircuitBuilder<F: ScalarField> {
 }
 
 impl<F: ScalarField> RangeWithInstanceCircuitBuilder<F> {
+    /// Convenience function to create a new [RangeWithInstanceCircuitBuilder] with a given [CircuitBuilderStage].
+    pub fn from_stage(
+        stage: CircuitBuilderStage,
+        builder: GateThreadBuilder<F>,
+        config_params: BaseConfigParams,
+        break_points: Option<MultiPhaseThreadBreakPoints>,
+        assigned_instances: Vec<AssignedValue<F>>,
+    ) -> Self {
+        Self {
+            circuit: RangeCircuitBuilder::from_stage(stage, builder, config_params, break_points),
+            assigned_instances,
+        }
+    }
+
     /// See [`RangeCircuitBuilder::keygen`]
     pub fn keygen(
         builder: GateThreadBuilder<F>,
diff --git a/halo2-base/src/utils/mod.rs b/halo2-base/src/utils/mod.rs
index 66f91166..54c88491 100644
--- a/halo2-base/src/utils/mod.rs
+++ b/halo2-base/src/utils/mod.rs
@@ -521,7 +521,10 @@ pub mod fs {
 mod tests {
     use crate::halo2_proofs::halo2curves::bn256::Fr;
     use num_bigint::RandomBits;
-    use rand::{rngs::OsRng, Rng};
+    use rand::{
+        rngs::{OsRng, StdRng},
+        Rng, SeedableRng,
+    };
     use std::ops::Shl;
 
     use super::*;
@@ -596,7 +599,7 @@ mod tests {
 
     #[test]
     fn test_get_lower_32() {
-        let mut rng = OsRng;
+        let mut rng = StdRng::seed_from_u64(0);
         for _ in 0..10_000usize {
             let e: u32 = rng.gen_range(0..u32::MAX);
             assert_eq!(Fr::from(e as u64).get_lower_32(), e);
@@ -606,7 +609,7 @@ mod tests {
 
     #[test]
     fn test_get_lower_64() {
-        let mut rng = OsRng;
+        let mut rng = StdRng::seed_from_u64(0);
         for _ in 0..10_000usize {
             let e: u64 = rng.gen_range(0..u64::MAX);
             assert_eq!(Fr::from(e).get_lower_64(), e);
diff --git a/halo2-ecc/src/fields/fp.rs b/halo2-ecc/src/fields/fp.rs
index f7022eb9..c26d8cc6 100644
--- a/halo2-ecc/src/fields/fp.rs
+++ b/halo2-ecc/src/fields/fp.rs
@@ -45,7 +45,7 @@ impl<F: ScalarField, Fp> From<Reduced<ProperCrtUint<F>, Fp>> for ProperCrtUint<F
     }
 }
 
-// `Fp` always needs to be `BigBigPrimeField`, we may later want support for `F` being just `ScalarField` but for optimization reasons we'll assume it's also `BigBigPrimeField` for now
+// `Fp` always needs to be `BigPrimeField`, we may later want support for `F` being just `ScalarField` but for optimization reasons we'll assume it's also `BigPrimeField` for now
 
 #[derive(Clone, Debug)]
 pub struct FpChip<'range, F: BigPrimeField, Fp: BigPrimeField> {