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 Cotter Pin 1/16" x 1" $17.13 Seachoice 01006 Lock Washer, #8 $15.43 Phillips Tapping Screw - Pan Head, #8 x 3/8" $12.60 Phillips Tapping Screws - Flat Head, #14 x 2" $41.13 Stainless Fender Washer #10, .062" Thick, OD 1" $48.06