M6 M7 M8 flange nuts - stainless steel serrated - set of 4-20 - free UK post
They have a serrated surface. The M6 & M8 nuts are sold in sets of 4, 8, 12, 16 or 20 nuts, while the M7 nuts are sold in sets of 2, 4, 6, 8 or 10 nuts. The hex size for the M7 nuts fits a 10mm spanner.