Because of the taper, a pipe can only screw into a pipe fitting a little distance before it jams.
Straights, Union Ball Joints, Pipe Fittings, Fittings
1 1/2 250 RR BLACK UNION DOM
Pipe Fittings - Bronze Unions - 2 125# NPT UL Listed
How to Install a Galvanized Union Fitting
Uxcell 1/4PT Male x G1/4 Female Thread 304 Stainless Steel Hex
The NPT cast pipe fitting is used for connecting and extending two male threaded pipes. The joint has three pieces, including threaded connections,
Cast Pipe Fittings Union - 1 NPT Female Fitting Stainless Steel 304, Class 150
Union Pipe Fitting
XtremepowerUS 1-1/2 in. PVC MPT x Slip Socket Flush Union Fitting for Pool Pump (2-Pack) 90115-H - The Home Depot
XtremepowerUS 1-1/2 in. PVC MPT x Slip Socket Flush Union Fitting for Pool Pump (2-Pack) 90115-H - The Home Depot
Union, JIC Fitting – Reliable Fluid Systems
PlumbShop Brass Compression Union, 1/2-in OD, 1-pk