Stainless Steel Button Head Bolt

These are high grade stainless steel button head screws. They'll never rust and they're really good at not getting seized. You should still grease them though.

Button head is more compact than a socket head, great for anywhere where you need extra clearance or just want a prettier bolt. 

M5 is commonly used on bikes for mounting water bottle cages, cable stops, rack and fender eyelets, as well as on various levers, derailleurs, seat clamps etc. 3mm tool surface. 

M6 is used for mounting V brakes and cantilevers to frames/forks, as well on various components. 4mm tool surface. 

M8 bolts are used on some seat post clamps (like our basic seatpost) and a few other places. 5mm tool surface.