Hex nuts with lock washer often referred to as keps or K-lock nuts,these nuts have a free-spinning lock washer to resist loosening once fastened
nuts with tooth washer have teeth that bite into the surface when tightened

Package include:
163cs 8-Sizes #4-40 NUC #6-32 NUC #8-32 NUC #10-32 NUF(fine thread) #10-24 NUC 1/4"-20 NUC 5/16"-18 NUC 3/8"-16 UNC Keps ( K-lock) Nuts Assortment Kit;Come with the plastic box:
List(Type,,Quantity)：
K-lock nuts #4-40 UNC 40PCS
K-lock nuts #6-32 UNC 30PCS
K-lock nuts #8-32 UNC 25PCS
K-lock nuts #10-32 UNF 20PCS
K-lock nuts #10-24 UNC 20PCS
K-lock nuts 1/4"-20 NUC 15PCS
K-lock nuts 5/16"-18 UNC 10PCS
K-lock nuts 3/8"-16UNC 3PCS
Packing contents:
MCMASKE 163PCS 8 Kinds #4-40 to 3/8"-16 Stainless Steel Keps ( K-lock) Nuts Assortment kit Packed in a plastic box