B-Line Eaton series imperial cable tray and ladder, 4" Height, 10.66" Length, 18" Width, 18" and 9" Tray widths, Series 2-5 straight reducer, Aluminum

It's the transition piece that takes an 18 inch wide tray down to a 9 inch wide tray in a straight line, keeping the run centered rather than offset. Eaton B-Line model 4A-18-SR09, Series 2-5, aluminum, 4 inch side rail height and 10.66 inches long in the direction of the run. Use it where the number of circuits drops off partway along a run and you want to step the tray width down instead of continuing full width.

Straight. The 4A-18-SR09 is a straight reducer, meaning both tray sizes stay on the same centerline through the transition. If your job needs one side rail to stay flush in line (running tight against a wall or matching an existing support layout), a straight reducer will not do that; you'd want an offset or right/left hand reducer instead.

It's CSA certified. That matters on Canadian projects and on institutional or utility specs that call for agency-certified tray components throughout the run, fittings included, not just the straight sections.

Plan on the tray system's splice plates and bolt kits at each end of the reducer, ordered separately to match your Series 2-5 aluminum tray. The reducer itself is the transition body, 18 inches at the wide end, 9 inches at the narrow end, 4 inches deep. Confirm your splice hardware matches the same series and rail height before you get to the transition point.

2.9 lb. Being aluminum, it adds essentially nothing to the load on your hangers, so a single electrician can set it in place without a second pair of hands. Support the fitting per your tray support layout the same as any other 10.66 inch section of run.

Aluminum is the choice where weight and corrosion resistance drive the spec, such as outdoor runs, coastal sites, plant environments and long spans between supports where you don't want the dead load. This reducer is aluminum, so it should be matched with aluminum tray of the same Series 2-5 family; mixing materials at a splice invites dissimilar metal corrosion and usually breaks the tray manufacturer's system spec.