I too have a 3c Kel-lite. I sleeved it with the appropriate pvc and am running 2x18650's with the xenon 5cell maglite bulb. A great improvement. You have to notch the sleeve to clear the switch guts, but everything else is pretty straighrt forward. Also, you can take a mag plastic reflector and cut it down if your kel-lite reflector is as bad as mine was. To clear everything you need to remove the blue gasket, but line the edge of the existing reflector (metal one) with electrical tape or she'll be on all the time. A stretch of the spring (or an appropriate size bolt) and your good to go.