B-Line Eaton series imperial cable tray and ladder, 4" Height, 33.0625" Length, 12" Width, Series 2-5 horizontal bend, Aluminum, 90° Angle, 24" Radius

That is exactly what it is built for. The 4A-12-90HB24 is a 12 inch wide, 4 inch loading depth aluminum horizontal bend, so it matches a 12 inch wide ladder tray with 4 inch side rails. Mixing widths or rail depths at a fitting means the rails will not line up at the splice, so the straight sections joining it need to be 12 inch wide, 4 inch deep aluminum as well.

Allow 33.0625 inches for the fitting. That is the overall length dimension of the 24 inch radius, 90 degree bend, so lay out your straight sections and hanger points off that number rather than off the 24 inch radius alone. Support is normally required within a short distance of each side of a fitting, so plan a hanger on each leg.

It carries CSA certification, so it is acceptable on work inspected to Canadian requirements. Aluminum construction also means it can be used in the damp and corrosive locations where painted steel tray gets rejected.

Order the splice plates and bolts separately. The 4A-12-90HB24 is the Series 2-5 horizontal bend section itself, so budget one set of splice connectors per joint, two for a bend dropped into a continuous run, plus your hangers or trapeze supports.

A horizontal bend like this 90 degree, 24 inch radius piece turns the run left or right while the tray stays flat, which is what you use to route around a column or change direction along a ceiling. A vertical elbow (inside or outside) is what you need when the tray has to rise or drop, for example up over ductwork or down a wall to a panel. They are not interchangeable, so confirm which plane your turn is in before ordering.

Quote B-Line 4A-12-90HB24. In that designation the 4A is the 4 inch aluminum rail, 12 is the tray width, and 90HB24 is the 90 degree horizontal bend at a 24 inch radius.

The fitting weighs 11.525 lb. At that weight a single installer can set it on trapeze hangers overhead, which is part of why aluminum tray gets specified over steel on long ceiling runs.