Material: the penny head glass stopper is made of high-quality borosilicate glass and annealed at 800 degree Celsius ,can be heated directly in an open flame and can withstand typical laboratory thermal variations in Chemistry processes like heating and cooling.
Design:1.heavy wall design——This glass stopper is heavy wall designed,made by hand-blowing to ensure uniform wall thickness;
2.Penny head design——for easy gripping；
3.Hollow design and closed bottom —— Laboy glass stoppers are lightweight yet very strong to reduce chipping and breakage, thus minimizing replacement costs.
Use: This Hollow glass stoppers precision ground glass stoppers are used to close glassware items including Boiling flasks,volumetric flasks,Separatory funnels, and cylinders to Keep air and water out of a reaction for uncontaminated reaction testing. The frosted, precision-ground glass surfaces make a good seal when properly greased and are extremely versatile.
Interchangable:The glass stopper has a 1:10 taper, it can fit any glassware with female joint which has the same taper and same outside diameter as long as the apparatus to which they are attached does not interfere. For example, a 24/40 joint stopper will fit into a 24/40 or/ 24/29 flask.But for the 24/29 flask,the ground glass joint will protrude (40 - 29) 11 mm into the flask.
Question:Do I need to greese the joint stopper
Answer:If you plan to heat your materials, you need to make sure that air and water are excluded from the system, and/or you want to make sure the joint does not freeze, then you must do so.