I've been using Knight Red Hot's for several years.
Why? I wanted a better nipple to replace the factory issue cheapies, they where available at a local shop and the proved to be very reliable.
I'm a paper puncher and I notice nipples only last 200-300 shot's before gas cutting begins to open the groups..
My source just dried up,,Sportsmens Whrs. closed,, so I'll be on a quest by next spring for a different replacment