diff --git a/src/Mesh.cpp b/src/Mesh.cpp
index 85b171a..4036ecf 100644
--- a/src/Mesh.cpp
+++ b/src/Mesh.cpp
@@ -101,7 +101,7 @@ namespace floatTetWild {
 	}
 
 
-	void Mesh::one_ring_edge_set(const std::vector<std::array<int, 2>> &edges, const std::vector<bool>& v_is_removed, const std::vector<bool>& f_is_removed,
+	void Mesh::one_ring_edge_set(const std::vector<std::array<int, 2>> &edges, const std::vector<char>& v_is_removed, const std::vector<char>& f_is_removed,
 	        const std::vector<std::unordered_set<int>>& conn_fs, const std::vector<Vector3>& input_vertices, std::vector<int> &safe_set)
 	{
 		// std::vector<int> indices(edges.size());
diff --git a/src/Mesh.hpp b/src/Mesh.hpp
index 31b4493..744bb42 100644
--- a/src/Mesh.hpp
+++ b/src/Mesh.hpp
@@ -189,8 +189,8 @@ class Random
 
         void partition(const int n_parts, std::vector<std::vector<int>> &tets_id) const;
 
-        static void one_ring_edge_set(const std::vector<std::array<int, 2>> &edges, const std::vector<bool> &v_is_removed,
-                          const std::vector<bool> &f_is_removed, const std::vector<std::unordered_set<int>> &conn_fs,
+        static void one_ring_edge_set(const std::vector<std::array<int, 2>> &edges, const std::vector<char> &v_is_removed,
+                          const std::vector<char> &f_is_removed, const std::vector<std::unordered_set<int>> &conn_fs,
                           const std::vector<Vector3> &input_vertices, std::vector<int> &safe_set);
 
         inline int t_empty_size() const {
diff --git a/src/Simplification.cpp b/src/Simplification.cpp
index 18a8f2f..981a9f2 100644
--- a/src/Simplification.cpp
+++ b/src/Simplification.cpp
@@ -31,8 +31,8 @@ void floatTetWild::simplify(std::vector<Vector3>& input_vertices, std::vector<Ve
     if (skip_simplify)
         return;
 
-    std::vector<bool> v_is_removed(input_vertices.size(), false);
-    std::vector<bool> f_is_removed(input_faces.size(), false);
+    std::vector<char> v_is_removed(input_vertices.size(), false);
+    std::vector<char> f_is_removed(input_faces.size(), false);
     std::vector<std::unordered_set<int>> conn_fs(input_vertices.size());
     for (int i = 0; i < input_faces.size(); i++) {
         for (int j = 0; j < 3; j++)
@@ -214,7 +214,7 @@ bool floatTetWild::remove_duplicates(std::vector<Vector3>& input_vertices, std::
 
 void floatTetWild::collapsing(std::vector<Vector3>& input_vertices, std::vector<Vector3i>& input_faces,
         const AABBWrapper& tree, const Parameters& params,
-        std::vector<bool>& v_is_removed, std::vector<bool>& f_is_removed, std::vector<std::unordered_set<int>>& conn_fs){
+        std::vector<char>& v_is_removed, std::vector<char>& f_is_removed, std::vector<std::unordered_set<int>>& conn_fs){
 
 #ifdef FLOAT_TETWILD_USE_TBB
     std::vector<std::array<int, 2>> edges;
@@ -503,7 +503,7 @@ void floatTetWild::collapsing(std::vector<Vector3>& input_vertices, std::vector<
 
 void floatTetWild::swapping(std::vector<Vector3>& input_vertices, std::vector<Vector3i>& input_faces,
         const AABBWrapper& tree, const Parameters& params,
-        std::vector<bool>& v_is_removed, std::vector<bool>& f_is_removed, std::vector<std::unordered_set<int>>& conn_fs) {
+        std::vector<char>& v_is_removed, std::vector<char>& f_is_removed, std::vector<std::unordered_set<int>>& conn_fs) {
     std::vector<std::array<int, 2>> edges;
     edges.reserve(input_faces.size() * 6);
     for (int i = 0; i < input_faces.size(); i++) {
diff --git a/src/Simplification.h b/src/Simplification.h
index fa18634..8339b6b 100644
--- a/src/Simplification.h
+++ b/src/Simplification.h
@@ -17,15 +17,15 @@ namespace floatTetWild {
             const AABBWrapper& tree, const Parameters& params, bool skip_simplify = false);
     bool remove_duplicates(std::vector<Vector3>& input_vertices, std::vector<Vector3i>& input_faces, std::vector<int>& input_tags, const Parameters& params);
     void collapsing(std::vector<Vector3>& input_vertices, std::vector<Vector3i>& input_faces, const AABBWrapper& sf_tree, const Parameters& params,
-                    std::vector<bool>& is_v_removed, std::vector<bool>& is_f_removed, std::vector<std::unordered_set<int>>& conn_fs);
+                    std::vector<char>& v_is_removed, std::vector<char>& f_is_removed, std::vector<std::unordered_set<int>>& conn_fs);
     void swapping(std::vector<Vector3>& input_vertices, std::vector<Vector3i>& input_faces, const AABBWrapper& sf_tree, const Parameters& params,
-                  std::vector<bool>& is_v_removed, std::vector<bool>& is_f_removed, std::vector<std::unordered_set<int>>& conn_fs);
+                  std::vector<char>& v_is_removed, std::vector<char>& f_is_removed, std::vector<std::unordered_set<int>>& conn_fs);
     void flattening(std::vector<Vector3>& input_vertices, std::vector<Vector3i>& input_faces, const AABBWrapper& sf_tree, const Parameters& params);
 
                     bool is_out_envelope(const std::array<Vector3, 3>& vs, const AABBWrapper& tree, const Parameters& params);
     Scalar get_angle_cos(const Vector3& p, const Vector3& p1, const Vector3& p2);
 
-    void check_surface(std::vector<Vector3>& input_vertices, std::vector<Vector3i>& input_faces, const std::vector<bool>& is_f_removed,
+    void check_surface(std::vector<Vector3>& input_vertices, std::vector<Vector3i>& input_faces, const std::vector<bool>& f_is_removed,
                        const AABBWrapper& tree, const Parameters& params);
 
     void output_component(const std::vector<Vector3>& input_vertices, const std::vector<Vector3i>& input_faces, const std::vector<int>& input_tags);