These Forgefix Flat Penny washers, have a 25mm outside diameter. The washers are bright zinc plated for increased corrosion resistance, & have been given the name Penny Washer due to their similarity in size to an old penny. Washers provide a smooth surface for the nut or bolt to bear on, making it less likely to loosen as a result of an uneven fastening surface. The main purpose of a washer is to distribute the load under a bolt head or the nut face. APPLICATION: On all manner of bolting applications. Can be used with all types of bolts & nuts. Zinc coatings prevent oxidation of the protected metal to create a longer lasting finish. It does this by forming a barrier & by acting as a sacrificial anode if this barrier is damaged. Zinc oxide is a fine white dust that (in contrast to iron oxide) does not trigger a breakdown of the substrate&8217;s surface integrity as it is formed. The zinc oxide, if left intact, can act as a barrier to further oxidation, in a way similar to the protection afforded to aluminum & stainless steels by their oxide layers. Flat Penny Washer ZP M6 x 25mm Box 500