The 1/2" metal t-valve is an all-purpose t-valve with 1/2" threaded connections on each end - perfect for electronic bidet seat installation.

The t-valve can screw directly on to shut-off valves that have 1/2" threads.  

Top: 1/2" female thread which connects to the shut-off valve
Side: 1/2" male thread which connects to the bidet hose
Bottom: 1/2" male thread which connects to the toilet supply hose

OPTIONAL 3/8" adapters.  

The female adapter would be used to connect this t-valve to a 3/8" shut off valve at the wall.

The male adapter would be used to connect this t-valve to the 3/8" toilet supply hose.

Add both adapters if you have a skirted toilet and want to use a t-valve at your shut-off valve.