diff --git a/xs/src/libslic3r/Flow.hpp b/xs/src/libslic3r/Flow.hpp
index cc8f90723..430a6197d 100644
--- a/xs/src/libslic3r/Flow.hpp
+++ b/xs/src/libslic3r/Flow.hpp
@@ -12,13 +12,13 @@ constexpr auto OVERLAP_FACTOR = 1.0;
 
 /// Enumeration for different flow roles
 enum FlowRole {
-    frExternalPerimeter,
-    frPerimeter,
-    frInfill,
-    frSolidInfill,
-    frTopSolidInfill,
-    frSupportMaterial,
-    frSupportMaterialInterface,
+    frExternalPerimeter        = 0b1,
+    frPerimeter                = 0b10,
+    frInfill                   = 0b100,
+    frSolidInfill              = 0b1000,
+    frTopSolidInfill           = 0b10000,
+    frSupportMaterial          = 0b100000,
+    frSupportMaterialInterface = 0b1000000,
 };
 
 
diff --git a/xs/src/libslic3r/Surface.hpp b/xs/src/libslic3r/Surface.hpp
index 1495d7215..17e232d7c 100644
--- a/xs/src/libslic3r/Surface.hpp
+++ b/xs/src/libslic3r/Surface.hpp
@@ -6,7 +6,17 @@
 
 namespace Slic3r {
 
-enum SurfaceType { stTop, stBottom, stBottomBridge, stInternal, stInternalSolid, stInternalBridge, stInternalVoid };
+/// Surface type enumerations.
+/// As it is very unlikely that there will be more than 32 or 64 of these surface types, pack into a flag 
+enum SurfaceType { 
+    stTop            = 0b1, 
+    stBottom         = 0b10, 
+    stBottomBridge   = 0b100, 
+    stInternal       = 0b1000, 
+    stInternalSolid  = 0b10000, 
+    stInternalBridge = 0b100000, 
+    stInternalVoid   = 0b1000000
+};
 
 class Surface
 {
diff --git a/xs/src/libslic3r/SurfaceCollection.cpp b/xs/src/libslic3r/SurfaceCollection.cpp
index 45f805c73..a629ebffb 100644
--- a/xs/src/libslic3r/SurfaceCollection.cpp
+++ b/xs/src/libslic3r/SurfaceCollection.cpp
@@ -100,6 +100,19 @@ SurfaceCollection::filter_by_type(SurfaceType type)
     return ss;
 }
 
+SurfacesPtr
+SurfaceCollection::filter_by_type(std::initializer_list<SurfaceType> types)
+{
+    size_t n {0};
+    SurfacesPtr ss;
+    for (const auto& t : types) {
+        n |= t;
+    }
+    for (Surfaces::iterator surface = this->surfaces.begin(); surface != this->surfaces.end(); ++surface) {
+        if (surface->surface_type & n == surface->surface_type) ss.push_back(&*surface);
+    }
+    return ss;
+}
 void
 SurfaceCollection::filter_by_type(SurfaceType type, Polygons* polygons)
 {
@@ -173,15 +186,19 @@ void
 SurfaceCollection::keep_type(const SurfaceType type)
 {
     // Use stl remove_if to remove 
-    auto ptr {std::remove_if(surfaces.begin(), surfaces.end(),[type] (Surface& s) { return s.surface_type != type; })};
+    auto ptr {std::remove_if(surfaces.begin(), surfaces.end(),[type] (const Surface& s) { return s.surface_type != type; })};
     surfaces.erase(ptr, surfaces.end());
 }
 
 void
 SurfaceCollection::keep_types(const SurfaceType *types, size_t ntypes) 
 {
+    size_t n {0};
     for (size_t i = 0; i < ntypes; ++i)
-        this->keep_type(types[i]);
+        n |= types[i]; // form bitmask.
+    // Use stl remove_if to remove 
+    auto ptr {std::remove_if(surfaces.begin(), surfaces.end(),[n] (const Surface& s) { return s.surface_type & n != s.surface_type; })};
+    surfaces.erase(ptr, surfaces.end());
 }
 
 void 
diff --git a/xs/src/libslic3r/SurfaceCollection.hpp b/xs/src/libslic3r/SurfaceCollection.hpp
index 085c16b68..1c948aea5 100644
--- a/xs/src/libslic3r/SurfaceCollection.hpp
+++ b/xs/src/libslic3r/SurfaceCollection.hpp
@@ -22,6 +22,7 @@ class SurfaceCollection
     template <class T> bool any_internal_contains(const T &item) const;
     template <class T> bool any_bottom_contains(const T &item) const;
     SurfacesPtr filter_by_type(SurfaceType type);
+    SurfacesPtr filter_by_type(std::initializer_list<SurfaceType> types);
     void filter_by_type(SurfaceType type, Polygons* polygons);
 
     /// deletes all surfaces that match the supplied type.