Have used these at adapters for Schraeder valves but they're great for adapting touring racks to 120-126 rear triangles and helping to pinch fender bolt tabs to eyelets.
These do the job, but should be anodized for corrosion protection. I just had to replace a tube after a pinch flat, and could not get the corroded stem saver off the old stem...corrosion was so strong that the stem ripped out of the damaged tube, as I tried to remove the stem saver. I had to limp home with low pressure to prevent the new presta tube from extruding through the Schrader hole.
All I have to say is I'm glad I switched to presta valve tubes using these stem savers on my 1979 Takara Sport Road Bicycle, because I use a pair of 28mm Continental Super Sport Plus tires that require a maximum pressure of 115 psi.
They work, and the price ins't too bad, but they could be done better. The rim at the end made too much bulk around the valve hole where the rim tape is already doubled, and the thick stem to tube connection is. I slid the adapters on from the outside, and tightened down the nut on the presta stem to hold it in place. They could stand to be bit longer too. They come shrin wrapped to a card and the plastic is very difficult to get off, I had to scrape it away with a knife. Not bad product, but there's room to iprove.
Used these on an older Trek hybrid bike that has 700cc tires but holes for schrader valves. Fits perfect and works as advertised. Don't need to worry about 'aneurisms' anymore.
I converted my daughters 20 in. bike to Presta using these and now I don't need to worry converting the frame pump on my bike to Schrader. One stem for everybody and one less thing for me to worry about. That's worth the price right there.