The 1620 Rack Ear Kit allows the Mackie Onyx 1620 mixer to be mounted in a standard 19" rack, where it will work conveniently. The 1220 mixer will take up 12 rack spaces, and you should allow an extra 1 or 2 rack spaces above to make your connections. The kit contains two rack ear brackets and four screws (longer than the original screws, with a captive washer).

Rackmount Ears for Mackie Onyx 1620 Mixer, 12 Rack Spaces