10x15x4

[rootar]

its not the volume its the diameter of the balls in the bearings and how far they have to travel each revolution of the bearing. not gonna go into detail because im on meds right now but basically a smaller outter diameter bearing with the same size balls as a bearing with a larger outer diameter will not have to travel as far per revolution which means less wear and load on the bearing, which is reason to choose the 8x16 over the 10x19 as it should last longer.