The Tap HSS 5x0.8 & Drill 4.2mm 2-Piece Set is a combination tool set designed for threading and drilling. The set includes: Tap HSS 5x0.8: This is a high-speed steel (HSS) tap with a 5mm diameter and a 0.8mm thread pitch. It is used for creating internal threads (tapping) in materials such as metal, plastic, or wood, allowing screws or bolts to be securely fastened into the material. Drill 4.2mm: This is a drill bit with a 4.2mm diameter, designed for pre-drilling holes before tapping. The 4.2mm size is typically used to create a hole that will be threaded by the included 5mm tap. Together, these tools are ideal for projects requiring precise threading and hole creation, often used in metalworking, automotive, or other industrial applications.