Online Parts Store › Nylon Insert Locknut - Stainless 5/16-18 Image 1 of 1 Nylon Insert Locknut - Stainless 5/16-18 $18.01 18-8 Stainless Steel. Add To Cart Added! 18-8 Stainless Steel. You Might Also Like Nylon Flat Washer 1/2", 0.62" Thick, OD 1-1/4" $36.72 Stainless Fender Washer #10, .050" Thick, OD 3/4" $18.58 Seachoice 01533 Hex Nut, 1/2-13 $66.78 Phillips Tapping Screw - Truss Head #8 x 3/4" $17.19 Stainless Cotter Pin 5/32" x 1" $51.08