I said that and linked to the OP linked laser, I felt like including the extra info for anyone interested as 301 and 303 units are more common than the OP linked laser, also the OP laser may not be the same diameter at the tail cap threads as the 501b, the Chinese are bad about changing things from batch to batch and from copycat maker to the next, granted it looks like it should fit, but he will have to try and see.The laser linked in the OP is not a 301, 302 or 303 laser. It is a 501B sized host that already has a tail cap switch. That was the reason I didn't try the 501B tail cap with it when I first pulled mine out. But, I put it back in the bottom of a box full of lasers and didn't get around to checking it again until late.
That's great news and helps a lot. Thanks, much appreciated!I just now tried the 501B tail switch with the laser you linked to and they DO interchange. I'm sorry, but I had to dig it out of the bottom of a box full of lasers and get a tail cap from a 501B to try on it. So, if there is some remote switch on a 501B that you can find it should work fine with that laser.