The H-S precision system is one of the most popular and has been around a long time, hard to beat them and hard to find them. AI magazines are very common and used by many bottom metal suppliers - Badger Ordanance also makes a wonderful assembly that uses the same AI clip. The exchange rate is great for buying MADE IN THE USA now.... Wolverine (MB) can get you the bottom metal by Badger and I think a couple of shops in Alberta can too...