Retaining RingThese screwdriver bits have a collar that acts as a stopper, preventing the bit from following the screw head into the drywall. The depth stop design can limit the screw penetration and damage the panel, once the collar comes into contact with the plasterboard, the drill bit cannot advance. PH2 screwdriver Made of high strength S2 alloy steel, these screwdriver bits are very durable. Heat treated to resist breaking and wear, impact resistant tool steel for maximum durability with a 1 or 4" hex shank for use in bit holders. Head MagneticThese screwdriver bits are with magnetic head, so they can firmly fix on the screw.Strong magnetic, can easily suck the screws when used.Bright color of the retaining ring allows you to observe clearly and easily, which is useful for your work. Widely UsedThese screwdriver bits have a wide range of applications, with 1 or 4 inch hex shank, designed to fit any n any electric drill and cordless drill for normal use.