Snap on fxkP extensions -- what's going on here?

[catalytic]

I just picked up a basically NOS FXKP6 extension, and I have a really stupid question. I've never seen an FXKP-series before, but it has a square-shaped retainer ball. The ball does not seem to want to depress in order to allow a socket to be fitted, but I don't see a release button like in the L (locking) series. So, what's the obvious thing I'm missing that's preventing me from getting a socket on this thing, and what's the general deal with the "P" in the FXKP series?

 

[yogitech]

That's a locking pin extension. You have to depress the pin in order to instal and release the socket. Carefull using it with anything that doesn't have a receiving hole in the drive end of the socket, you gonna have a hard time getting it out!

 

[The Ratchet Man]

Some impact guns have the same pin retention. Not really practical in an automotive environment but absolutely necessary in an envrionment where a dropped socket just can't happen. We use pin retention at work since you might be 40' in the air with guys working underneath you.

 

[catalytic]

Thanks for the replies. So there are sockets made with a hole specifically for this pin?

 

[reptilezs]

Thanks for the replies. So there are sockets made with a hole specifically for this pin?

cornwell and most impact sockets