M3 X .5 X 18MM Flat Hd Socket Cap Screw Purple Anodized , These are manufactured from 7075 Aircraft Quality Aluminum Heat treated to a T-6 condition.
Fastener Dimensional Data for Metric Aluminum Flat Head Cap Screws - Blue Aluminum: (Size: 3mm)

For Reference Only:

Metric Aluminum Flat Head Cap Screws - Dimensional Data
Metric Machine Screw Threads - Dimensional Data

Find Coordinating nuts and washers for your Metric Aluminum Flat Head Cap Screws below:

Nuts:

Blue Aluminum Locknuts

Washers

Blue Countersunk Flat Washers