GearWrench 8921 21 Piece 3/8-Inch Drive (20mm) Metric Pass Thru Ratchet Set Includes: Gear Ratchet handle, (7) SAE Vortex sockets (3/8-Inch, 7/16-Inch, 1/2-Inch, 9/16-Inch, 5/8-Inch, 11/16-Inch and 3/4-Inch), (10) Metric Vortex sockets (10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm and 19mm). Also includes: 1/4-Inch Dr. Gear Ratchet adapter, 3/8-Inch Dr. Gear Ratchet adapter, Vortex Pass-Thru 3-Inch extension (Designed to reach into deep recesses making deep sockets obsolete). Pass-thru sockets work when even deep sockets are too short A fine tooth ratchet and socket system that changes from a pass-thru system to a conventional ratchet handle with interchangeable 1/4-Inch and 3/8-Inch drives that allow for the use of standard sockets Up to 40-Percent stronger by eliminating drive tang and up to 50-Percent thinner than conventional ratchet systems