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 Stainless Fender Washer 5/8", .109" Thick, OD 2" $37.03 Phillips Tapping Screws - Flat Head, #8 x 3/4" $12.91 Phillips Tapping Screw - Pan Head, #14 x 3" $61.60 Phillips Tapping Screws - Oval Head, #10 x 2" $27.33 Square Tapping Screw - Oval Head #8 x 1-1/2" $54.12