B-Line Eaton series strut channel, 3.25" channel height, 240" channel length, 1.62" channel width, Steel, 12 Gauge, B11 channel type, Pre-galvanized

Pre-galvanized (mill galvanized) steel is meant for dry interior work: mechanical rooms, above ceilings, electrical rooms, indoor process areas. The zinc goes on the coil before roll forming, so the cut ends and any field cuts are bare steel. For exterior runs, parking structures, wash-down areas or anything with chemical exposure, specify hot-dip galvanized after fabrication or stainless instead of this pre-galvanized B11.

Gauge is wall thickness, and it sets the load the run will carry. This B11 is 12 gauge steel, the heavier of the two common strut thicknesses, which is what you specify for trapeze hangers carrying multiple conduits or pipe, longer unsupported spans, and pipe racks. 14 gauge is the lighter-duty option used for short spans, single-conduit supports and light equipment mounting. Combined with the 3.25 inch deep profile, the 12 gauge B11 is the heavy end of the strut range.

Functionally it does the same job, but it is not the same part. B11 is a single 3.25 inch deep channel section with one open slot face, not a welded-back-to-back assembly. If your drawing calls for a back-to-back double channel with slots on both faces, B11 will not satisfy it, since only one side is open. Where the spec simply calls for a deeper, stiffer single-slot channel, the 12 gauge B11 is the part.