An SDS drill bit is a masonry bit designed for concrete drilling that is used with a rotary hammer drill. The acronym SDS stands for "Slotted Drive Shaft" or "Slotted Drive System". The SDS bit is placed into the end of the drill and is held in place by twisting the chuck of the drill, locking the bit in the collar. The SDS masonry bit is not held solidly in the chuck of the drill but slides up and down like a piston. The slots in the shank of the SDS bit accept the two ball bearings in the spring-loaded chuck of the hammer drill and will remain chucked until disengaged by the user. There are different types of SDS bits, including SDS, SDS-Plus, SDS-Max, SDS-Top, and SDS-TE-S. The SDS Plus range is shorter in length and is tailored to lighter duty work and smaller diameter holes, while SDS Max bits are thicker and ideal for larger hammer drills, making bigger sized holes.