These retainers are lighter weight, less expensive and provide the reliability of metal retainers. We're putting them on all of our TARC rockets.

they work just as good as the aluminum ones and less expensive

Just like the Estes 29mm PS II Motor Retainers, the Estes 24mm PS II Motor Retainers accumulate exhaust residue and can melt slightly when in contact with the exhaust plumes supersonic shock wave, like sparks and partially lit fuel residue. To make them last longer, simply wrap the exterior of the lock nut with ablative material, I use HVAC aluminum duct tape, from Home Depot, or any hardware store. Showing no bare grey plastic, they will look like metal nozzles when wrapped tightly, with this tape. I also use Teflon tape on the male threaded internal mount, 2-3 layers will suffice. These thin ablative layers are light weight, do not alter the C/G that much and can be easily replaced when worn.