This Fender Pop-in Caster 4-pack is a convenient way to add portability to your guitar amplifier. This design simply pops in and out of the mounting cups with a ball-bearing swivel design. GearNuts players never head to a gig without these. Push them in to move the amp, pull them out to put your amp flat on the stage. You'll love this Fender Pop-in Caster 4-pack. Fender Pop-in Caster 4-pack Features: 4-pack of casters for your Fender amp Casters and mounting cups included Easy to use Convenient swivel design Upgrade your amp with this Fender Pop-in Caster