B-Line Eaton series imperial cable tray and ladder, 4" Height, 11.5" Length, 18" Width, 18" and 12" Tray widths, Series 2-5 left reducer, Aluminum, 12

It is a left reducer that transitions an 18 inch wide aluminum cable tray down to a 12 inch wide tray, keeping the 4 inch loading depth through the transition. The reduction happens on the left side, so the right side rail stays in a straight line and only the left rail steps in. Overall length through the fitting is 11.5 inches.

Handing on a reducer is called out looking in the direction of the run. Model 4A-18-LR12 is the left-hand version: the left side rail angles in while the right rail runs straight. If your straight edge needs to be on the left instead, you want the matching right reducer in the same 18 to 12 inch, 4 inch deep configuration. Getting this backwards puts your tray offset to the wrong side of the support, so confirm which rail must stay in line before ordering.

The fitting is a 12 inch radius. That radius sets the minimum bend the conductors see as they pass through the width change, so if your cable spec calls for a larger training radius than 12 inches, this reducer is too tight and you need a longer radius fitting. For most power and control cable in 18 inch tray, 12 inch is the common stock radius.

Aluminum tray and fittings hold up well in damp, coastal, and wash-down environments because they do not rely on a coating the way painted or pre-galvanized steel does, and they are light to rig. Where the run needs high load capacity over long support spans, or where the environment is chemically aggressive, a steel or fiberglass tray system is the better call. The 4A-18-LR12 is an aluminum fitting only, so the whole run needs to be aluminum Series 2-5 for the splices to line up.

Order Eaton B-Line part 4A-18-LR12. Read as the manufacturer builds it: 4 inch deep aluminum, 18 inch nominal width in, left reducer, 12 inch radius. Distributors cross-referencing by width and hand should confirm the trailing LR for left and the 12 for radius, since the right-hand and other-radius versions share the leading digits.

The 4A-18-LR12 is supplied as the reducer fitting itself. Splice plates and bolt hardware for joining it to the adjoining 18 inch and 12 inch tray sections are separate items in the B-Line aluminum line, so plan on two splice connections per fitting when you build the material list.

It weighs 2.9 lb. Aluminum keeps the dead load low, so a single reducer adds almost nothing to your trapeze or strut supports, and one person can hold it in place while bolting the splice plates. Compare that to a steel fitting of the same 18 to 12 inch geometry if you are working off a ladder alone.