Darnell dual wheel piano casters are equipped with four sided double ball raceways.
Wheel Diameter: 2"
Wheel Width: 3/4"
Wheel Material: High Capacity Neoprene
Load Capacity Per Caster: 200 lbs.
Mount Height: 3"
Stem Dimension: 1/2" Dia x 1-1/8" Long
Supplied with cast-iron sockets
 
Uprights supplied with round sockets. 
Grands supplied with square sockets.