Can they run on 1 x 18650 ? just wondered because it looks like they have an extension .
If it is the same as everything else using that body - Ultrafire WF-500, Romisen RC-T6, Romisen RC-T5 then no. The extension is CR123 sized. It allows for dangerous things like running 1RCR123 and an 18650 but is intended to let you use 3 or 4 RCR123s.
I think.
I will let you know I guess. I have a body on order for a project involving a MC-E 
I dont know if anyone is still interrested in this topic, but is is exactly as Don said, the extension is as long as a 16430, see pictures.
TR-1200(short body, same TR-800 body) works with single 18650 with spacer or with 3x16340 or 1x18650 and 1x16340 witout spacers. If you plan to use 3x16340 check the maximum voltage of the led driver. TR-1200 perfectly works with 3x16340.
Welcome moniac, good to have you here.
Aloha and welcome to BLF moniac!