An assembly tool for inserting a slide ring or counter ring of a slide ring seal, in particular a running gear seal, cooperating with an elastic sealing body into an associated housing part, the assembly tool including a number of clamping elements formed as arcuate segments and an assembly O-ring, wherein the clamping elements engage around the slide ring or counter ring, and around the sealing body and the assembly O-ring in a manner that corresponds to the circumferential length thereof, and the clamping elements are advanceable in the direction of the housing part in order to mount the sealing body within this housing part.