I can tell you that the 250 are a differnt size than the 350's......But the terms are rated 4560 and 6075.......I don't know which ones you are shooting, but try the collars for a 250 if you are using the 4560's, and the 350's for the 6075's.....

CX also makes their version of the pin nock....Those would would be better for what you're wanting.