Whatever checks you buy make sure they are made with the same material thickness as standard checks whcih your mold is made for. Aluminum work fine for magnum revolvers and lighter rifle loads, but with high pressure/high velocity shooting, I'd stick with brass, copper or guilding metal, which is what Hornady and Gator checks are made of.
Tread lightly before buying a gas check maker. If you don't have cheap stock to make the checks from and if the check maker isn't a high quality unit which makes checks fast enough to suit you and is capable of lasting a long time. It may not be worth the purchase price. Most shooters can buy a lifetime supply of gas checks for the price of a check maker, and they are high quality if you get them from Gator or Hornady. (RCBS/Lyman are Hornady mfg.)
