Intermountain's reefers are built with sn injection-moulded plastic underframe on which trucks with couplers are mounted, and an injection-moulded plastic body glued to the underframe. The cars are delivered with plastic wheel sets with semi-high flanges of lesser quality than that of Micro-Trains, and truck-mounted couplers. The couplers work fine together with Atlas's couplings but are less reliable coupling and uncoupling with Micro-Trains couplings. Older cars may have couplers that cannot couple automatically.
The cars are designed so that the height from rail top to the coupler mounting platform is 7.1mm. There are holes in the floor that fit the Micro-Trains #1015 and #1023 couplers. I don't like the #1023 coupler as the coupler spring is in compression when the car is hauled, this can lead to the cars bouncing back and forth in a long train.
I like to use wheel sets with small flanges and #1015 couplers. This type of coupler is designed to be used without a shim for a mounting platform height of 7.1mm above rail top, so it fits perfectly here.