ASC Engineered Solutions 21/2X21/2X11/4 BLK MI TEE

It's a reducing tee: two 2-1/2 inch runs and a 1-1/4 inch branch. All three openings are female pipe thread (FPT), so pipe or nipples thread into the fitting rather than over it. Use it where you're pulling a 1-1/4 inch branch off a 2-1/2 inch line.

Yes. The threads are cut to ASME B1.20.1, which is the standard NPT taper thread spec, so it mates with ordinary threaded black steel pipe and nipples. Dope or tape the male threads as usual; the seal is on the thread taper, not a gasket.

It carries UL/FM approval, which is the listing fire protection contractors and AHJs look for on threaded fittings. The 2-1/2 x 2-1/2 x 1-1/4 configuration is a common cross-main to branch-line takeoff. Confirm your hydraulic design calls for a 1-1/4 inch branch before ordering.

Black malleable iron is uncoated and will rust in wet, oxygen-rich service, so it's normally used on natural gas, fuel oil, air, and closed or fire protection systems rather than open potable water. For domestic water you'd want galvanized or a different material entirely. Black fittings like this one are the standard choice for gas piping and threaded sprinkler work.

Standard (STD) class, rated per ASME B16.3. That's the 150 class malleable iron family, as opposed to the heavier 300 class extra-heavy fittings. If your spec calls for XH or 300 class, this is not the right fitting.

It's dimensioned to ASME B16.3, the same standard other malleable iron threaded fitting makers build to, so the face-to-center lay lengths interchange with any other B16.3 standard-class fitting of the same size. That matters when you're cutting nipples to a drawing or replacing one fitting in an existing run.

Malleable iron cast to ASTM A-197, the standard material spec for cupola malleable iron pipe fittings. Malleable iron takes thread engagement and impact better than gray cast iron, which is why it's used for threaded work rather than brittle cast fittings.