I bought one of these. I couldn't get it to lock on the plugs, OS 8 and F. It is as though the crimps that hold the cap to the plug are not correct. I could get the cap on the plug, but there was not enough travel in the contact piece to maintain a positive connection.

I took it back to the LHS and they tried it on every plug they sell. Didn't work. They then tried the other Sullivans they had on the rack, none of them worked. I think a bad batch made it past their QC dept.

I have since found a small spring at the local hardware store that fits a plug perfectly. I soldered my wire to it, covered it with shrink wrap, and now have a reliable connection. It is really easy to put on and off as well.