I spend a lot of time working on AR-15s and find that small parts like this retaining ring which is important for keeping the dust cover post in place are also easy to loose if dropped. Most places sell them for as much as $2.00 each so now I now have a goodly number on hand should I either drop one or just not get one with parts kits I ordered. They cost me about 10 cents each. I will buy again when the need arises.
