HVAC Tool Kit:Dual Size Schrader Valve Core Remover/Installer and A Square Head Ratchet Wrench for System Port Service Set Dual size valve core remover installer change 1/4 and 5/16 inch port extract core in charged systems ratchet wrench for system port valve stem opening or closing port square head 4 sizes great service tool kit for the professionals in HVAC Solid Forged Brass/steel construction, designed solid to last. alternative source for high quality service tools