B-Line Eaton series imperial cable tray and ladder, 6" Height, 27" Length, 24" Width, 24" and 18" Tray widths, Series 2-5 horizontal reducing tee, Alu

The Eaton B-Line 6A-24-18-HT12 horizontal tee joins 24 inch and 18 inch tray widths, so it both branches the run and reduces width in one fitting. Overall width of the fitting is 24 inches and the length/depth is 27 inches. If every leg of your run is the same width, you want a straight horizontal tee instead of this reducing version.

It is a 12 inch radius fitting. That radius is what governs the minimum bend the conductors see as they turn through the tee, so it is the spec to check against the cable manufacturer's minimum bending radius for the largest conductor in the tray. Smaller radius tees (common in control and instrument runs) will not satisfy large power cable.

It is UL Classified. That is the rating carried on the fitting, and it is the one an inspector or institutional spec writer will ask about on a cable tray installation.

A reducing tee like the 6A-24-18-HT12 does both jobs in one piece: it branches the 24 inch run and steps the branch to 18 inch tray. Using a straight tee plus a separate reducer adds two more splice points, more hardware, and more length to the run. Go with the separate reducer only when the width change has to happen somewhere other than at the branch.

Horizontal only. The 6A-24-18-HT12 is a horizontal reducing tee, meaning it branches the run in the flat plane. Changing elevation calls for a vertical inside or outside bend, not this fitting.