How high does the seat go?

The seat adjusts from about 17.3 to 23.5 inches, which covers most bench and low work heights. Check your work surface before buying if you need a taller seat.

Does it hold up for heavier users?

The steel frame is rated to 340 lbs. That is higher than most rolling shop stools, which typically top out around 250 to 300 lbs.

The listing does not state locking casters. On smooth concrete the stool can roll when you push off, so plan for that or add a mat.

What are the trays for?

Three trays hold tools, fasteners and parts, with the lower tray adjustable up to about 4.75 inches. They sit under the seat, so they cut into legroom.

Is it good for a garage or a salon?

It suits garage and workshop use best. The backrest and swivel also work for a salon or tattoo station, but the trays and casters are built for shop floors.