New Tuning Wrench for  Autoharp, Hammered Dulcimer, Harp, Chromaharp, and Zither. When tuning or changing a lot of strings you want a tuning wrench that in comfortable in your hand. Unlike the 3 inch handle on the Trophy tuning wrenches this Oscar Schmidt tuning wrench has a 4 inch handle with about a 1 inch diamante, total length almost 6 inches. This makes it much easier to work with instruments that have lots of strings. It may be a few dollars more, but well worth it. Opening is 3/16 in square.