Supersedes the original horn, which has been discontinuedby Mercedes.
The new horn requires a short wiring harness to adapt this to your vehicle and must be spliced at the time of installation (see below)
To install: Plug the new harness into horn, and cut the larger plug off the opposite end. Then, cut the plug off the end of the vehicle wire harness and slice the two wires together, using electrical tape to insulate the connections.(These instructions are straight from Mercedes Benz)