Lakeside Products MagnaPen - Whelping Box Extension Pen (Extension only)Please note: This product is a whelping box extension piece for a MagnaBox Whelping Box. Lakeside Products Whelping box extension, The MagnaPen Extension pen, is the perfect addition to the MagnaBox Next Generation Professional Whelping Box for dogs. The whelping box extension pen 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