Clamp(1) for an external fixator, preferably of the quick attachment type, comprising: a plurality of attachments(2； 3) for blocking bars and/or bone screws； a connector(5), provided with an at least partially threaded stem (50), which passes through and connects in series said plurality of attachments(2； 3)； at least one first attachment(2) comprising two arms (20； 21), connected by a C-shaped flexible bridge (22)； said stem (50) passing through said first attachment(2) in an intermediate position between said flexible bridge(22) and the opposite free ends of said arms (20； 21)； wherein, at the free ends, said arms(20； 21) define a screw housing seat (23) for a bone screw, said screw housing seat being selectively configurable, varying the deformation of the flexible bridge (22), to clamp bone screws having different diameter.
