Comparison : Item # Custom, Custom N.T.U. Series Nylon Insert Lock Nut
Item # pn-5510, N.T.U. Series Nylon Insert Lock Nut - Heat Treated - 1-14 - - Phos. & Oil
Item # pn-5511, N.T.U. Series Nylon Insert Lock Nut - Heat Treated - 1 1/4-12 - - Phos. & Oil
Item # pn-5512, N.T.U. Series Nylon Insert Lock Nut - Heat Treated - 1 1/2-12 - - Phos. & Oil
Item # pn-5513, N.T.U. Series Nylon Insert Lock Nut - Heat Treated - 1 3/4-12 - - Phos. & Oil