K-9 Keeper Exercise Pen w/Door Four Paws Exercise Pens are gold zinc plated for maximum durability. All pens have 8 panels, 24" in width. Our patented, inter-locking system securely holds the panels in place and assures the safety of pets. K-9 Keeper Exercise Pens feature a full convenient door with security latches for easy walk-through access. K-9 Keeper Exercise Pens can be configured in many different positions and fold flat for easy storage and portability. Four Paws Exercise Pens are gold zinc plated for maximum durability. All pens have 8 panels, 24 in width. Our patented, inter-locking system securely holds the panels in place and assures the safety of pets. K-9 Keeper Exercise Pens feature a full convenient door with security latches for easy walk-through access. K-9 Keeper Exercise Pens can be configured in many different positions and fold flat for easy storage and portability.