The Rockville WH4 zinc plated steel caster wheels just made the life of a DJ and/or gigging musician that much easier! We at Rockville understand the importance of mobility When playing live shows or gigging. With the New WH4 casters you can give your back A rest and at the same time decrease tear down and load time! These heavy duty 3” swivel casters will hold up to 350 lbs. And are simply a necessity for when line arrays and dual or Quad 18” subs are just too heavy for one person to move around. These casters are zinc plated and are made from steel. The locking mechanism minimizes movement from heavy vibrations and the swivel housing make it that much easier to move around. These caster can be used for speakers, subwoofers, monitors, rack cases or anything else that is too heavy to lift.