In the past century there were a lot of 2xD flashlights on the market, and the Ranex SS was one of them. They were advertised as stainless steel, but maybe it was just chromed tin. These lights were sold in Hema and Gamma outlets.
I created this thread because I did not want to hijack @XxyourQuaff thread Maglite Upgrade, Cheap Upgrade Alternatives? with too much information about upgrading a non-Maglite incandescent flashlight. This upgrade is not about adding a massive pill or something like that for shedding the heat of the upgrading emitter, but rather converting it as painless as possible (for my wallet) from 2xD to 2x18650.
First of all the light itself. As you see, size and shape are comparable to a Maglite D2.
Unlike the Maglite, the switch mechanism is wedged between two plastic spring washers, and it is an actual Omten-like switch.
To accommodate the 18650’s in a D-sized body I took a piece of 139 mm length from a regular standard PVC pipe 32x26 mm as the “outer case”.
The actual size was 32.2x26.2 mm. The best way to hold the 18650 cell’s was using the extension tubes from my Warsun M900.
Those were 26.6 mm OD, and that’s where an adjustable reamer comes in handy 
The PVC combo fits the body, but something has to be sorted out in the tailcap department. BTW you don’t have double vision, I bought three Ranex lights.
Left is new, right is original.
I removed the original spring, and drilled a M5 thread in the tailcap. Put in a M5x10 mm bolt and secured that on the inside with a M5 nut. A M5 nut has an “outer diameter” of 9 mm, so I managed to “wiggle” a 10 mm spring over that nut. On the opposite side I did the same with a stepped washer of the right size that I found in my spare parts box. Mind you, everything came out of my spare parts box.
Instead of putting a cherry on top of the cake, I swapped the incandescent light bulb with a Ruiandsion P13.5S XP-G2 1-9V led upgrade, rated at 300 lumen.
And if I don’t fry it, I might even considering putting in a 55/525 lumen LiteXpress module.