Biomed Scientific Magnetic Stir Bar PTFE Magnetic Stirrer Mixer Stir Bars High Magnetism Teflon Coated Stirrer Rod Type-C Set 7pcs/Pack, White

Solid, strong, and very well balanced.

These are worthy of constant use!

Perfect sizes and strong magnetic connection.

Exactly what was needed

Performed as expected

Work like a charm

I use stir bars a lot. I needed some and just happened to come across this kind. Some times you have to use these in really aggressive chemicals. Ptfe is not completely chemically resistant. They do last a long time though. Picture one old kind on the right new on the left. Also in this picture you can see a rough size comparison. Well these new ones are about double the weight of others I have. I would advise caution just dropping these in glass containers I have broke beakers doing that in the past with other ones that weigh less. The magnetism however is also double strength roughly. It is very strong. Picture two you can see the biggest one in use on a hotplate stirrer. It had no problem holding on at the highest rpm the hotplate would go. Some times you need really vigorous agitation. For that these will be great you can see a wild whirl pool as proof. Adding to the positives the price is really reasonable. I do believe this is ptfe. You can usually tell by taking off a small bit and burning it the fluorine smell is un-mistakable. I had a hard time smelling it over other chlorine smells that were lingering in the area. I put it in hot nitric acid to be sure for 30 mins and let it sit for another 12 hours. Its perfectly fine still. The only things I didn't like were that some of the coatings were not uniform. As well as these magnets seemed to always default to the flat side, and they were a tiny bit un balanced, but it was not really a problem. All good for budget stir bar kit though.

These are not worth buying. Tried only spinning a small amount of water with these and every time the magnet disconnected. They don't have enough weight or a strong magnetic pull to keep them in place.

Cumplen su función, el precio es algo elevado