I'm not sure of this, but I suspect .002, 309 or 321 is the same stuff (respectively) no matter the brand, but some sell 321 as good for 1800 and others as 2000
USAKM - 321 - 2000F - 309 - 2240F
ENCO - 321 - 1800F - 309 - 2100F
Jantz - 321 - 1900F - 309 - 2200F
Having said all that, I think Ken is right. I meant to say WE only use 309 - specifically because we are doing other people's blades. I'm pretty sure if it was my own blades, I'd be using 321 on a lot of steels too.
Rob!