This shut-off valve works great and appears to be of good quality; the operation of the slider to adjust flow is very smooth and can be moved with one finger. The item comes with washers and a small amount of teflon tape (though I can't comment on the latter since I used my own). I used my own thicker washer (obtained at a hardware store under the shower parts category) instead of one of the two washers the valve came with - one of the ones it came with got pushed down the wall side of the pipe I was affixing this to, and my thicker one (same as the thinner in all aspects but thickness) seemed to work better. It could be that I tightened it too far when using the thinner washer on the wall side; when installing it again with my thicker washer I was more cautious how far I tightened the wall side. I am getting no leakage from the valve edges nor the slider. The non-threaded portion of the valve is just a little over an inch so it does not extend the showerhead out from the wall much farther than without the valve, when installed.

So I can now choose the shower pressure from blastingly powerful down to off. My partner prefers the valve at a middling slider position, which, combined with the moen banbury 5-spray 4-inch showerhead I am using (with regulator plastic "X" retainer and inner o-ring broken out for full flow from the showerhead itself, a showerhead I recommend) yields the perfect shower pressure and is adjustable, as I said.

I bought this valve to reduce water pressure on a toilet supply line to a bidet attachment.

The first valve I received had a very slow leak from the middle slot where the adjustment knob sits. I contacted the seller and they were immediately responsive, sending a replacement valve that same day. The second valve works perfectly.

To answer some common questions:
-The valve can be used to shut off water completely OR reduce water pressure depending upon how far you move the knob, which is easy to adjust.
-The valve comes with one washer to be seated in the female end so look for it when you unpack the box.
-Plumber's (Teflon) tape shouldn't be needed on braided supply lines with a washer (like under a toilet or sink) as they're compression fittings. Tape may actually compromise the seal on these connections. Hand-tighten, then use pliers to gently tighten an additional 1/4 - 1/2 rotation if needed.

For bidet attachment installation, I put the valve between the splitter (water line tee adapter) and the supply line to the bidet. See pics.

Four stars just because the first valve was a dud but the second valve is great and seller customer service was impeccable so overall I'm pleased and would recommend it. Just monitor it closely for a day after installation to confirm it works well.

Looks steady and good value for its price

As mentioned in other reviews, this product is mostly sturdy chrome. Peering inside, I can see the shutoff valve is plastic, but the plastic seems high quality.

The valve has no markings to indicate whether it is open or closed. I used nail polish to mark the open setting. The valve can shut off the water 100%, making it easy to forget to turn the spigot off when you leave the shower. As I have installed mine at the end of a hand held flexible hose, this could be disastrous.

This was super easy to install. Based on other reviews, I bought Teflon tape for the job, but I haven't needed to use it so far. Here is how I installed it in 15 seconds:
1.Remove hand held shower head from flexible hose (no tools needed)
2.Screw shut-off value onto the flexible hose. Tighten it only slightly.
3.Screw hand held shower head onto other end of shut-off valve. Again, barely tighten it.

I did not tighten the connections because wanted to see just how bad the leakage was. I reckoned I'd be taking it apart again in a minute. As it happens, it didn't leak at all!

Observations:
- Although I can shut the water off 100%, I let it drip to avoid putting too much pressure on the flexible hose.
- if I had installed it on the other end of the hose, it wouldn't matter so much if I left the valve closed and the water on. I wouldn't want to chance it, though.
- Positioning the valve on the hand shower head makes it easy to adjust so I doubt I will move it to the wall end of the hose.
- Test your connections before buying Teflon tape.

I am pleased with this purchase and I will recommend it to relatives.

Easy to attach in between existing shower stem and head (provided that your pipe size and threads are typical/standard), and definitely helps save water. More than just an on-off switch, it can be used to proportionately reduce the water flow too, so you can open it up all the way for a water-blasting rinse, or close it down part way for less pressure/flow, or close it all the way to stop water flow altogether. The control knob moves smoothly and reduces the water flow proportionately, but does leak a little (just a drip/trickle), so you won't want to use this as a replacement for your regular on-off valves. However, since it's only intended for use while actually showering, a little dripping isn't a big deal.

Some important notes about potential water temperature changes when using this device... The temperature and amount of hot water may be affected when significantly reducing or shutting off water flow for long periods, as less water flow can allow pipes to cool or change the proportion of hot vs. cold water moving through the pipes, thus affecting the output temperature. Users with on-demand (tank-less) water heaters may experience even more variability as the sensors in the heater have to adjust the heat with changes in water flow, and may not even heat the water at all if the flow falls below a certain level, resulting in a slow cool off or even surprise blast of cold water when turning the pressure back up. Best practice for tank-less water heater users - either on or off; part way will probably not work well for you, and you'll probably have to experiment to see what works.