What are the differences between different forms of washers?
Flat Washer (MM) – Standard Bolts & Nuts Sdn. Bhd.
M16 Flat Penny Washer (Pack of 1) Large OD Plain Wide Round Metal Alloy Steel Washers for Screws – Zinc Coated Plated Galvanized Heavy Duty Certified Standart ISO7093 M16 (17mm x 50mm) :
Stainless Steel Plain Washer, Round, Size: M2 To M52