Quoted from "gezzas525"

No its a 1/4 NPT thread on a BIX III.

Just for clarification purposes I wanted to make it clear that three different thread specs exist on the BI series of rads. 1/4 NPT, 1/4 BSPP, and a universal thread. The only one compatible with Aqua Computer fittings is the BSPP. The universal thread is debatable as it only hangs onto the BSPP fitting by a thread or two.