These are the best snail lock back up pads that can be purchased. Designed primarily to withstand the pressure of automated C Frame and other automated machines, these are made with many premium features: 5/8-11 Brass Threads. Rubber insert around the Brass thread to reduce vibrations, and to break away in case the machine jams. This saves serious repairs to the machines. When used by hand on grinders and polishers, they just might last forever!