Drill & Tap Set - 1/4" Tapered Pipe Tap and Drill Set. If your vehicle’s axle breather hole is to large for the 1/8" fitting included and required to install the PCP Diff Cleaner. This drill and tap kit will open it up to the next larger size, 1/4" pipe tap. Purchase reducer (1/4" to 1/8") to complete installation. Kit includes 1 tap drill, 1 1/4" pipe tap (NPT) and instructions.