Bearings - NSN Parts Catalog
Bearings NSN parts Federal Supply Group number 31Mounted and unmounted anti-friction and plain bearings.
A bearing is a machine element that constrains relative motion to only the desired motion, and reduces friction between moving parts.
For a more technical outline of bearing types and functionality see Bearings (Wikipedia)
Bearings - Sub Categories
Unmounted Antifriction Bearings
FSC 3110
MIL Parts: A, B, C, F, G, H, I, L, M, O, P, Q, R, S, T in this category
Unmounted Plain Bearings
FSC 3120
MIL Parts: A, B, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, W in this category