Seems like quite a good deal, even after the relatively expensive delivery. I've considered buying deskmats from here in the past, and can can confirm they're not always on sale. I haven't seen them promote this anywhere, just went to the website recently and they were all $10.
I think these are almost all 900x400x4mm, but some of the descriptions are missing since they're shared with the relevant keycap descriptions.
I bought two for $34.10 delivered.
Thanks OP, picked up a pair of deskpads too
I really didn't need these lol