Lakeside Products MagnaBox Pen Extension KitDescription Lakeside Products MagnaBox Pen Extension Kit Designed for use with the MagnaBox Whelping Box The MagnaPen Extension pen, is the perfect addition to the MagnaBox. This pen extension kit easily attaches to the front of the whelping box and uses the same hook and slot joints as the whelping box. The MagnaPen incorporates the same 1 3 and 2 3 height doors for easy access and control. It is simple to clean and keep clean. FDA approved, HDPE