diff --git a/AntiAircraftGun/AntiAircraftGun/SetAntiAircraftGunsGeneric.cs b/AntiAircraftGun/AntiAircraftGun/SetAntiAircraftGunsGeneric.cs
index 1270d41..9807595 100644
--- a/AntiAircraftGun/AntiAircraftGun/SetAntiAircraftGunsGeneric.cs
+++ b/AntiAircraftGun/AntiAircraftGun/SetAntiAircraftGunsGeneric.cs
@@ -56,7 +56,7 @@ namespace AntiAircraftGun
         /// <returns></returns>
         public int Insert(T antiAircraftGun, int position)
         {
-            if (position < 0 || position > _places.Count) return -1;
+            if (position < 0 || position >= _places.Count) return -1;
             _places.Insert(position, antiAircraftGun);
             return position;
         }
@@ -67,7 +67,7 @@ namespace AntiAircraftGun
         /// <returns></returns>
         public T Remove(int position)
         {
-            if (position < 0 || position > _places.Count) return null;
+            if (position < 0 || position >= _places.Count) return null;
             if (_places[position] == null) return null;
             T removed = _places[position];
             _places.RemoveAt(position);
@@ -82,12 +82,12 @@ namespace AntiAircraftGun
         {
             get
             {
-                if (position < 0 || position > _places.Count) return null;
+                if (position < 0 || position >= _places.Count) return null;
                 return _places[position];
             }
             set
             {
-                if (position < 0 || position > _places.Count) return;
+                if (position < 0 || position >= _places.Count) return;
                 _places.Insert(position, value);
             }
         }