I bought it for my Novation SL61MK3 and it fitted perfectly.
I'm a bit sceptical it would fit well in 73 key keyboard, since it is fairly stretched already on 61 key keyboard with fairly thin sides, so if you need it for 73 keys, YES, it'll probably stretch but looking for slightly bigger one maybe a safer bet.
As for the material used, it is made of quality and stretchy spandex that probably won't wear out very fast, and judging on feel, it would probably save you from a minor liquid spills too.
In overall, I'm happy to buy it and recommend it to others.