Ideal for MDF / all fibre boards / chipboard, matches most common board sizes. Clamps the boards fast. Will not pull apart under load. Does not blister the board on insertion. This pack of Prodrive drive recess countersunk flat heads are constructed from a durable case hardened, 45mm in length and come partially threaded. They have coarse thread and underhead ribs. They're ideal for a range of DIY applications.