M4 x 18mm Thumb Screw (Low Type) in A1 Stainless - DIN 653

This is the thin type of knurled thumb screw, as it has no shoulder beneath the head, unlike the high type of thumb screws. The large head diameter allows these fasteners to be easily adjusted to a precise tightness by hand. They are frequently used in situations where routine maintenance is required, as they are quicker and easier to fit and adjust in comparison to fasteners which require a driver.