As a new caster, I was clueless about different mould designs etc. I have picked some up here and there and tonight cast up some with Lyman 4 cavity, Lee 2 cavity, and Lyman single cavity. I have learned that I prefer a two cavity over the 4 just due to the extra manipulation required to use the 4. The single cavity is easy of course but at 1/2 speed so I believe I am going to stick with 2 cavity moulds until I learn otherwise. Also learned that the fact that aluminum moulds heat up quicker is a nice little attribute of the Lee stuff. Lovin this stuff!