Stupid Drywall Question

Here's a sanding block, has small angled sides. They work great for tight areasView attachment 1716271930

I like that style. Looks like they left the abrasive off the corner too. I've never seen one like that in the stores I frequent. Most have one square edge and one 45 edge but has abrasive all over which is why I nip one of the edges off the 90.
I'll have to keep an eye out for one like you show.