It is a MRC CR-1, I have it feed with a maxijet 1200.
As far as a check valve, is this what you guyes are talking about?
http://www.premiumaquatics.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=M3-DCV&Category_Code=
I was also told about this Co2 regulator, it looks really nice but I...