B-Line Eaton series imperial cable tray and ladder, 6" Height, 14.892" Length, 30" Width, Series 2-5 vertical outside bend, Aluminum, 60° Angle, 12" R

The fitting's own radius is 12 inches. That sets the minimum curve the cable sees through the transition, so if your conductor's required minimum bending radius exceeds 12 inches, you need a larger radius fitting (B-Line builds these in larger radii for the same tray width). Large power feeders are the usual case where 12 inches is too tight.

Direction of the turn relative to the cable. A vertical outside bend, which is what the 6A-30-60VO12 is, carries the run up or down with the cables on the outside of the curve, so the tray bends away from the cable bundle. A vertical inside bend turns the other way, with the cable on the inside radius. Get it backwards and the fitting bolts up but the run turns the wrong direction at the transition, so confirm which way the run breaks before ordering.

This fitting is aluminum, which is the usual pick where you want corrosion resistance without paint or galvanizing, and where weight on the support structure matters. It has to match the rest of the run, though: mixing an aluminum fitting into a steel tray run creates a dissimilar metal joint at the splice and the bolt patterns are not interchangeable across material families. Keep the whole run in one material.

What you're ordering under MPN 6A-30-60VO12 is the vertical outside bend fitting itself, a 30 inch wide, 6 inch deep aluminum 60 degree outside bend on a 12 inch radius. Splice plates, bolts and the hangers or trapeze supports for the transition are separate line items, so add them to the order if you don't already have them on the job.