The quality of the fabric is very good but rather rough, the seat deserves a cushion for better comfort because after a few minutes of play we feel the chair shear under our legs (at the level of under the knees). Otherwise the seat is great for getting a racing feeling, I'm on Dirt rallye 2.0 and it's just incredible, the downside is that it's not very stable, a mat could be a solution, to be seen.
A child who is 135cm tall is going to have a problem with the crankset being 5cm too far away, so I folded the stand back a bit but had to hold it in place with a strap so it wouldn't move (the crankset, not the child), then put 2 good cushions on it so he could play and it was fun.
Then there's no support to adapt to add the gear lever and a handbrake, so I'm planning to make one myself. I hope this helps.
I'd recommend this seat because for the price I think it's decent, but it could do with a few improvements.

It is a mesh fabric, probably nylon. You sit comfortably, quality is good