This is sold, but another member of the Mesa Boogie facebook group is selling one - view post.
Lightly used, early 90s original style kit with removable top access panel. Converts Mesa amps to a 4U (four spaces high) 19" rackmount format.
The newer version sells for $169, and does not have a removable top panel or cooling fan.
This fits 17" slanted-panel amplifiers, such as the Mark I, II, III, .50 Caliber, Studio .22, etc. Includes a removable 120V cooling fan.