General Description: This set of two hand valve lapping and grinding tools is designed for a perfect fit of the gas seat during advanced engine overhauls. The double-sided suction cups are made of UV-resistant synthetic rubber, allowing for efficient final wetting of the assembled part. These tools are suitable for a variety of valves, including those on lawnmowers, chainsaws, and cars, with dimensions of 5/8\", 13/16\", 1-1/8\", and 1-3/8\" (1.6 cm, 2.9 cm, 3.5 cm). Their ergonomic design ensures a comfortable grip and efficient use. Technical Specifications: Overall length: 8.9\" (22.6 cm) and 8.3\" (21.1 cm) Cup sizes: 5/8\", 13/16\", 1-1/8\", 1-3/8\" (1.6 cm, 2.9 cm, 3.5 cm) Instructions: To use these tools, remove any carbon deposits from the valves and wipe them clean. Install the valve in its guide, firmly press the appropriately sized cup onto the valve head, and gently rotate the tool handle between your palms until a suitable finish is achieved. It is recommended to apply abrasive (not included) to the valve seat or surface, being careful to keep the abrasive away from the top surface of the valve to ensure proper inhalation.