B-Line Eaton series imperial cable tray and ladder, 6" Height, 11.5" Length, 24" Width, 24" and 18" Tray widths, Series 2-5 right reducer, Aluminum

It transitions a 24 inch wide cable tray down to an 18 inch wide tray. The wide end matches 24 inch tray and the narrow end matches 18 inch, so it is the fitting you use where a run steps down in width rather than butting two different sizes together.

Yes, it matters. A right reducer takes the width off one side only, keeping the opposite rail straight through, so the run stays aligned along that edge. The 6A-24-RR18 is the right-hand version; if your run needs the offset on the other side or centered, you need a left or straight reducer instead. Confirm the direction against your tray layout before ordering, because a right reducer cannot be flipped without inverting the tray.

The fitting adds 11.5 inches of length to the run. Lay that into your straight-section takeoff when you are cutting tray to fit between supports, since the reduction happens across that 11.5 inches rather than at a single joint.

Aluminum is the usual pick where weight and corrosion matter, indoors or out, and where the run is being hung off a structure that you do not want to load heavily. This reducer weighs 3.86 lb, which is why aluminum runs go up fast with fewer hands. Steel tray is the alternative where you need higher load capacity or where the specification calls for it; the two are not interchangeable fittings, so the whole run has to be one material and one series.

Order it as 6A-24-RR18. The number reads directly: 6 inch depth, aluminum, 24 inch incoming width, right reducer to 18 inch.

It is CE marked. That is the certification held on record for this reducer; if your submittal calls for something else, verify against the manufacturer's listing data for the series.