The Wotow dogbone wrench is a very nice casting of zinc... well, a mixture that is mostly zinc probably. It is much heavier than cast aluminum would be, and the handle is very thick. So this wrench is the strongest little dogbone wrench that I have found. This beefy wrench weighs 117.8 grams. (Much sturdier than the 21-gram sloppily-cast alternatives on Amazon.) It is also a little longer than the other dogbone wrenches I have. This Wotow wrench is 4.160" from end-to-end.The casting is well-done. There are minimal ridges at the mold separations. The surface is uniformly textured, like it has been bead-blasted or tumbled smooth. I decided I would put it into service with zero modification, no clean up, no de-burring. It is nice. I like it, and I use it. Is heavier than I expected, and does not feel right for small delicate hand work. It looks strong enough to use on a bicycle… maybe I should test that.The 7mm square hole in the end of the wrench is useless to me. The other end has a slightly-distorted hexagonal hole - almost 8mm. There is no 6mm nor 7mm hex hole, so this wrench doesn't have the same "6-to15 mm" range that other wrenches have. But it is still a good wrench that gives you 8mm to 15mm sizes.The end with the hexonal hole in the end has 8mm, 15mm, 11mm, and 14mm hexagonal openings around the sides.The end with the 7mm square hole has 9mm, 13mm, 10mm, and 12mm hexagonal openings around the sides.This wrench is too heavy to dance in your fingertips, so it won't replace my favorite dogbone. However, it does feel comfortable in your hand. This is a well-made worth-owning good tool for situations where you don't have your toolbox or socket wrenches handy. Remember it is not steel, but it is pretty strong. (None of the dogbone wrenches are made of steel. That would be so cool.)Buy this Wotow dogbone wrench, and you won't be sorry.