I've used 3M 6001 and 60923 and can't tell a difference between the two other than the 6001 breathes a bit easier. This doesn't mean that either is the correct cartridge to use though. I also don't use a half mask, I use the 6800 full face along with a paint suit. Not even close to as good as a fresh air respirator but it is what it is. I guess the isocyanates can absorb into your skin, so want to keep that protected as best you can.