Great for tight areas ....8mm nut  with a 10 wrench head it is copper coated which is great for high temp areas

The nut is flanged  for strength

You are buying 8 nuts  which is what most air-cooled engines uses

M 8 - 1.25 Top Lock Flange Nut Class 10 Copper Plated

SPECIFICATIONS

DIAMETER : M 8

THREAD PITCH : 1.25

HEIGHT : 7.8mm

WRENCH SIZE : 10mm

FLANGE DIAMETER : 13.9mm