Review on PZRT Washer Bicycle Safety Retaining by William Chavez

They may be difficult to make, but these things seem ridiculously expensive for what you get. They keep your axle from slipping if someone loosens your cam or axle nut, or if they just come loose. This has never happened to me, but I like to prepare for the unexpected. Not all dropouts have holes for this, sometimes the tongue needs to be on part of the dropout itself. Consider which way the axle will fall out when it comes loose and you can find a way to prevent that with these washers. Two stars is what I think is a stupid price.