Features Vacuum sound flask: put the electric bell in the jar and you can hear a clear bell, then take out the air, the bell will gradually weaken until no sound is heard. Close the exhaust valve so students can observe. The bell is still ringing, but no sound is heard. More experiments: a cup of boiling water is discharged into the glass hood, and then pumped, you can see that the hot water in the cup is boiling again. In addition, this instrument can also be used for experiments such as vacuum source, evaporation glazing, vacuum coating and atmospheric pressure. Simple operation: The operation of sound physics demonstration is very simple, so students can have better and happier learning in class. MADE OF GOOD PVC - Adopting premium PVC material, the transparent bell can clearly demonstrate the electric doorbell inside, very easy to check. CONVENIENT CARRYING - Comes with light weight and compact size, the whole vacuum hood set is very convenient to carry outdoors. 1. Vacuum sound flask: put the electric bell in the jar and you can hear a clear bell, then take out the air, the bell will gradually weaken until no sound is heard. Close the exhaust valve so students can observe. The bell is still ringing, but no sound is heard. 2. More experiments: a cup of boiling water is discharged into the glass hood, and then pumped, you can see that the hot water in the cup is boiling again. In addition, this instrument can also be used for experiments such as vacuum source, evaporation glazing, vacuum coating and atmospheric pressure. 3. Simple operation: The operation of sound physics demonstration is very simple, so students can have better and happier learning in class. 4. MADE OF GOOD PVC - Adopting premium PVC material, the transparent bell can clearly demonstrate the electric doorbell inside, very easy to check. 5. CONVENIENT CARRYING - Comes with light weight and compact size, the whole vacuum hood set is very convenient to carry outside. Specification: Item Type: Vacuum Hood Material: PVC. Battery: 2 x AA batteries, supplied without batteries. Packing List: 1 x vacuum hood. 1 x Bell 1 x Vacuum Plate Package List 1 x Vacuum Bell Jar 1 x Bell 1 x Vacuuming Plate