Hi Craig, just a little question? I've got an ultra fire XML T6 in 5 mode.off eBay I've ordered a few things a 501b in red led,2 spare ultra fire 18650 batteries and a remote pressure switch.at the moment only the pressure switch has arrived yesterday.Is the end cap on the 501a smaller diameter than the XML t6?because i tried the pressure switch on my XML and it didn't quite fit,didn't want to force it on.but on the item description on eBay it said it fitted 501b,501a & XML. Im hoping the torch will arrive shortly its on the slow boat from China. picking up the kit abit at time before i ge