Park Tool SWR-8 3/8″ Drive Ratchet. The SWR-8 is an eight inch (20cm) long ratchet designed to drive any 3/8″ drive socket or bit as well as some Park Tool bottom bracket tools. Forged from alloyed steel and chrome plated for daily use the SWR-8 is reversible and features a quick release button to easily switch from one socket to another.