M4 is a metric screw thread size, and M4 screws made of polymer materials may be used in a variety of applications where a lightweight and corrosion-resistant fastener is needed. M4 screws have a 4 millimeter diameter and a thread pitch of 0.7 millimeters. Polymer materials are often chosen for their lightweight and corrosion-resistant properties, making them suitable for use in a variety of applications where metal fasteners may be too heavy or prone to corrosion. M4 screws are typically used in conjunction with M4 nuts and washers to secure objects together. Washers are flat rings that are used to distribute the load of a fastener and to prevent damage to surfaces. Nuts are used to fasten bolts and screws together and are typically tightened using a wrench.