The Galco Slip-on pads are the Cadillac of slip-on pads--and priced like it. A more reasonably priced quality alternative to the Galco is Galazan's Gamekeeper slip-on pads. The leather on the Gamekeeper pad is a darker brown color, a little stiffer and not as pliable as the Galco. I have a couple from both manufacturers and each serve their purpose. What I like about both is that when installed the velcro is covered by the leather flap--unlike others. Either one adds about 5/8" to LOP:
http://www.csmcspecials.com/Gamekeeper_Slip_On_Recoil_Pad_p/e0490.htm