Steel City BU 503 1 Inch Insulated Conduit Bushing, Rigid/IMC, Non-Metallic

The Steel City BU bushing is made for rigid conduit and IMC. It threads onto the conduit end to give wires a smooth insulated edge as they leave the raceway. It is not a fitting for EMT, which is not threaded.

Non-metallic. It is an insulating bushing, so it does not carry the bonding path. If your installation needs the conduit bonded at that termination, the bond has to be handled by the locknut, a grounding bushing, or a bonding jumper, not by this part.

Three trade sizes: 1 inch (BU 503), 2 inch (BU 506) and 3 inch (BU 508). Match the trade size to the conduit, not to the cable you are pulling.

Where a raceway ends and conductors leave it, the conductors need protection from the cut thread edge. That is the job of the BU bushing: it screws onto the male thread of rigid or IMC and presents a rounded, non-metallic throat instead of bare steel. Electricians commonly use one on each conduit landing in a panel, pull box, or wireway. If you also need the conduit bonded to the enclosure, use a grounding bushing instead, since this one is non-metallic.

Yes. BU 508 is the 3 inch trade size in the line and is threaded for rigid or IMC, so it goes straight onto a 3 inch rigid stub. The conduit thread still needs a locknut to secure it to the enclosure; the bushing protects the conductors, it is not the mechanical fastener.

No. The BU 503 is threaded for 1 inch rigid or IMC. EMT terminations use connectors rather than conduit threads, so you would need an insulated-throat EMT connector or an insulating bushing sized to that connector's threaded hub instead.