DangerDen's 3/8" blocks and 1/2" blocks use different threads, I know this because I asked them to send me 1/2" fittings to put in the Maze1C they had just given me. They said they would not fit, and that they'd just send me a 1/2" block instead. I haven't paid much attention to which size NPT they use (or if it's even NPT), I just run with what I have.
