diff --git a/zecsy.hpp b/zecsy.hpp
index 7626d6b..1910148 100644
--- a/zecsy.hpp
+++ b/zecsy.hpp
@@ -97,7 +97,7 @@ namespace zecsy
         std::unordered_map<comp_id, component_pool> pools;
 
         using archetype_signature = std::vector<comp_id>;
-        using entity_group = std::vector<entity_id>;
+        using entity_group = std::set<entity_id>;
 
         struct archetype_hash
         {
@@ -186,7 +186,7 @@ namespace zecsy
 
         std::vector<comp_id> key;
         auto& group = archetypes[key];
-        group.emplace_back(id);
+        group.emplace(id);
 
         return id;
     }
@@ -199,7 +199,7 @@ namespace zecsy
         std::vector<comp_id> key(comp_set.begin(), comp_set.end());
 
         auto& group = archetypes[key];
-        group.erase(std::remove(group.begin(), group.end(), e), group.end());
+        group.erase(e);
 
         if(archetypes[key].empty())
         {
@@ -279,8 +279,7 @@ namespace zecsy
             std::vector<comp_id> old_key(old_set.begin(), old_set.end());
 
             auto& group = archetypes[old_key];
-            group.erase(std::remove(group.begin(), group.end(), e),
-                        group.end());
+            group.erase(e);
 
             if(archetypes[old_key].empty())
             {
@@ -288,7 +287,7 @@ namespace zecsy
             }
 
             std::vector<comp_id> new_key(comp_set.begin(), comp_set.end());
-            archetypes[new_key].emplace_back(e);
+            archetypes[new_key].emplace(e);
         }
     }
 
@@ -311,13 +310,12 @@ namespace zecsy
             std::sort(old_key.begin(), old_key.end());
 
             auto& old_group = archetypes[old_key];
-            old_group.erase(std::remove(old_group.begin(), old_group.end(), e),
-                            old_group.end());
+            old_group.erase(e);
 
             std::vector<comp_id> new_key(comp_set.begin(), comp_set.end());
             std::sort(new_key.begin(), new_key.end());
 
-            archetypes[new_key].emplace_back(e);
+            archetypes[new_key].emplace(e);
 
             if(archetypes[old_key].empty())
             {