Will this product support modularity/customisation like purchasing a single pocket for the backside?

Hello, this product isn’t designed to be modular at this point but we do offer several models that are on our website (A-Series, D-Series, M-Series, T-Series, etc). We may design modular accessories that can be swapped in the future though. Thanks for asking!

Does it have lifetime warranty?

Yes, it has a limited lifetime warranty. You can refer to our website for the full details.

Do you sell just the sturdy rubber elastic? i want to install it on the d03? i like d03 for the id window but hate the cheap elastic that comes in it

I went to Dango's website and purchased a sturdy silicone band that works way better than the elastic band. Thats the only problem with this wallet (cheap elastic band( but it is still the best minimalist wallet that I have owned. Works great. Great value for $35.00.

How tight are the rails in this wallet supposed to be? Are they really tight and dont allow mivement once cards are inserted, or is there some some le

The rails are fairly tight, when all the cards are inserted. There is maybe 1/4 of a millimeter of play but the cards fit snug. Once one card is pulled out, then that hold the aluminum housing open, and you can freely access all of the cards.