M3 X .5 X 20MM 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 - Purple 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:

Purple Aluminum Locknuts

Washeres

Purple Countersunk Flat Washers