Jim, I am going to start out with a 9mm Caspian slide and frame. The only 9mm mags I have seen listed in Brownells are 9rd. from Colt and Metalform. I would like to have a 10rd. mag. One of the local matches I shoot has a 10rd. max. mag. capacity, any caliber larger than a .380. There are 10rd. mags. for the .38 Super, but I like the cheap 9mm stuff.