All standard wingnuts are A4 316 grade stainless steel for maximum corrosion resistance.
Some examples of the places each size are used on Sharks
M5 - Used on metric rudders & slide fixings
M6 - Foot stretchers pre 2018
M6 Nylon - Standard foot stretcher wing nut
M8 - Used on section plates
You are in Canada, and we have a Canadian website here.