Bosch 2608587442 HC8021 2-5/8" x 12" Spline Rotary Hammer Core Bit - Bosch brings constant innovation to concrete and masonry drilling. This spline thru-hole rotary hammer bits offer less vibration and quieter operation thanks to an efficient design that maximizes the power of the hammer. Its wave design transfers energy to bit more effectively for up to 40% faster drilling than its previous design.