I don't think you can run it without a reg unless you have a LP air tank. I've heard good things about the following regs (in no particular order):

Palmers Stabilizer (Of course!)
Evil Detonator
Bob Long Torpedo
Dye Hyper 2
Eclipse Star

I've used all of them except for the Hyper 2 on my various Spyder project markers. The Star and Detonator are definitely Low Pressure Regs (e.g. 400 or 600psi max output range) which may not be able to handle input from standard HPA tanks (800-850psi). I'm not too sure on this though so if someone else has the correct info on them I don't mind being corrected. I've never had a problem with either of them but then I've always used an Evil Scion tank which is an adjustable LP air tank. I had problems with the Torpedo when I ran CO2 through it. I couldn't get it to recharge fast enough as my ROF increased. It's still a good reg though. As for the Stab, I've yet to really put mine through its paces but that should change this weekend. I'm using the Female variant (via a modification) but all Stabs are generally rated highly for both CO2 and HPA so a male one should be good on the LPK.

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