The 1620i Rack Ear Kit allows the Mackie Onyx 1620i mixer to be mounted in a standard 19" rack, where it will work conveniently. The 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).