I use a t20 on my guns I have one with green led in and one with nv these were amazing little torches then I found out about the mods for them and it dubbled the range here is a pic of standard and mod t20 side by side
I have now got a got both t20s with the lens adaptor on and use the same lens for both total cost of mod
Lens adaptor £2.49
Lens £9.99