Ah, missed that, they've had so many versions, as you're about to find out:
There are two Maglite bulb socket types, PR and bi-pin, bi-pin is the newer socket type.
There are three Maglite incan bulbs, krypton, xenon, and bi-pin xenon; xenon is the newer bulb type that superseded the old krypton, bi-pin xenon includes an adapter so you can fit it into a PR socket.
Only bi-pin bulbs are being manufactured, the PR bulbs are being phased out.