Glass Penny Head Glass Hollow Stopper, 5 Pack

These come in super handy, continually. Not just for flasks, either - I've had to stopper various female joints due to mishap, poor planning, or just to prevent leakage while switching flasks or between uses of an addition funnel without a stopcock.These stoppers are nice and durable and the penny head means that the diameter is no larger than the joint they fit, so they stay pretty well out of the way. Pretty sure i can use them with 29/*, too, which is nice.

Perfect, had gotten the distillation kit a while back, these work good to close it off from atmosphere

I ordered Stonylab glass stoppers, but they don't have the Stonylab logo on the penny head. I am wondering if these are just some cheap counterfeit stoppers. I like Stonylab glassware and expect to receive the OEM version not some knockoff.I don't know how to grade these other than they do look like glass stoppers.

Finely made glass stoppers for the 24/40 taper, these are precision ground, symmetrical, and the glass is free of ripples or bubbles. And the price is right. Great for leaving a solution to rest for a few hours or overnight but not for more than a few days as the stoppers will eventually freeze.