It's a wrist rest - 1 month of use
Optional wrist rest, and indeed it is optional. Leatherette wrist rest, padded rather generously with foam. It hasn't moved in 1 month of use. Not that it's bad, just that it won't make a huge difference to your comfort for gaming sessions of any length (from 1 hour to 6 hours).
I manage to play without it (I play on an XL mouse pad from the UK brand IDgaming. I don't know the thickness of the mat, but it seems pretty standard, a long way from steelseries heavy, I'd say 3mm?
So if you're looking to save a bit of money, you'll have to pass, otherwise you won't be disappointed.
Next update in 6 months ;)