The Drill King X-Treme Tool Pro Series shock subs feature a simple, yet robust and proven design made from the best alloy steel. Major benefits include drastically reduced vibration and shock loading, and reduced maintenance to the rotary drive. Added life to the bit and DTH hammer is a given fact. Sizes available from 4- to 18-inch range. Call us today at 866-900-2487 or sales@drillking.net. www.drillking.net