B-Line Eaton series imperial cable tray and ladder, 4" Height, 13.25" Length, 18" Width, 18" and 9" Tray widths, Series 2-5 left reducer, Aluminum

It transitions an 18 inch wide aluminum tray down to a 9 inch wide tray, with the offset taken on the left side rather than split evenly. The run's left rail continues straight through and the right rail steps in. Rail height is 4 inches and the fitting is 13.25 inches long, so you need that much straight space between supports where the width change happens.

They are not interchangeable in a ladder tray run. On the 4A-18-LR09 the reduction is taken off one side so the left rail stays in line; flipping it inverts the rungs and the rail orientation. Determine the offset side from the direction of cable pull on the drawing and order the matching hand. If you need the narrow tray to line up on the other rail, you want the right-hand version.

Aluminum. That keeps it light (3.2 lb for the fitting) and it's the usual choice where corrosion is a concern or where the run is being carried up by hand. Keep the whole run in the same material as the straights and other fittings so you aren't mixing aluminum and galvanized steel at bolted splices.

The 4A-18-LR09 is the reducer fitting itself. Splice plates and their bolt sets are ordered separately per connection, and you need a pair at each end of the fitting, so budget two sets per reducer plus any hold-down hardware at the support it lands on.

Allow 13.25 inches of run length for the fitting, measured along the tray, and 18 inches of width clearance at the wide end. Rail depth is 4 inches. If your support spacing puts a hanger right at the transition, plan the trapeze to catch the wide end where the load is.

Order it as Eaton B-Line 4A-18-LR09: 4 inch rail, aluminum, 18 inch tray reducing to 9 inch, left hand. Anything reducing to a different narrow width or taken on the right side carries a different suffix.

It is CE marked. That is the certification held on record for the 4A-18-LR09 aluminum reducer.