Its a chair

The bolts snap after prolonged use.

I've used the following this listing before for replacement parts. Its $40 which is incredibly steep. It includes:

• Bolt
• Knob
• Washer
• Ball bearing
• Plastic arm guard
• Friction Clamp
• Metal Bar

However, others have indicated (Archived) the bolt itself can be found numerous places, including Lowes, Home Depot and Mendards. Sizes are: 1/4“-28 2-1/2”