The Jackhammer Driving Kit (JDK) is great for large projects where fast installation is desired. This kit comes with a driving bit and HSP-T4 hammer spacer. The jackhammer bit (OH-01) fits a standard 1-1/8” jackhammer chuck. The included HSP-T4 works with 4" × 4" wood posts. The purchase of an additional spacer may be required and will be noted with each product.