Junkin 6 Pcs Exercise Yoga Ball Bulk for Yoga Chairs Heavy Duty Ball for Balance Include Pump for Stretching Physical Posture Improves Balance

These are good and sturdy and easy to inflate, if a bit tiring. If you have a power pump, be sure to use it. The structure is thick and should hold up to abuse, if that's how they get handled.

I bought these as seating in my Jr. High classroom. The kids love them and I'm learning to tolerate them. They are fun and I even use one when Im working away from my desk. The only down side is that they lose air fairly quickly but I allow the kids to pu.p them up when needed - so win win for me.

My arms are sore from pumping up only one, but it wasn’t difficult. Pull out the white stopper, insert the pump, pump till full, replace the stopper. They are thick rubber, so they should hold up well. The rubber is smooth and the balls are a good size for kid use. It’s not large enough to use as a desk chair like one of the pictures tries to make it seem, but it works for yoga. And it’s not too big for young kids to use. Love that they come in a pack of six, so I can use them with my class! Good yoga balls all around!