Geekey features a new patent pending closed wrench where it has combined both Metric and Imperial sizes into one. The overall thickness is divided equally for the closed wrench allowing enough depth for adequate torque on hex bolts and nuts. The Imperial side fits 1/8, 3/16, 1/4, 5/16, 3/8, and 7/16 inch hex sizes. The Metric side fits M8 (13mm), M6 (10mm), M5 (8mm), M4 (7mm), M3.5 (6mm), and M2 (4mm) hex sizes (Note: 13mm also fits 1/2 inch). With this design approach the parallel fit won't destroy the hex head shape when tightening or loosening.