Patent, DIN 3123/ISO 3316.
Return tools for warranty replacement directly to KC Tool. All returns are subject to inspection prior to replacement.
The design of the locking mechanism is such that it will actually work with other brands of sockets (at least, what I have around, like SK). I've encountered other brands that don't work with different sockets, like Wera, which are also very difficult to operate. The Stahlwille operates easily.
By far my favorite locking extensions I own. Not as bulky as others and holds very well.