FREE SHIPPING! Two Replacement Battery Caps compatible with the Invisible Fence® Brand R21, R22, R51, & MicroLite™ receiver collars. Exact aftermarket reproduction of the Invisible Fence® Brand Power Cap®. Designed by Scott Touchton of Perimeter Technologies, Inc. (former chief engineer at Invisible Fence, Inc.) Just $10.99 per battery! We ship all orders within 1 day!