measuring - Does the outer diameter of 4.78 indicate an M4 or an M5 bolt? - Home Improvement Stack Exchange
TR knowledge base | Thread geometry - metric coarse
4mm x 20mm Extractable Dowel Pin H&G DIN 7979D - Non-Threaded Fastener Supplier | Caleb Components
Common M4 Fastener Screw and Bolt Sizes - MonsterBolts
Pack of 6, M4 x 18mm (4mm) A2 Stainless Socket Cap Screws with Free A2 Stainless Steel NYLOC Nuts (Pack of 6), Steel HEX Head : Amazon.co.uk: DIY & Tools