Rubber bungs of different sizes to seal/close test tubes/boiling tubes/conical flasks.
Yes, there could always be a leak in coolant tubes. Most tubes are made from rubber and rubber + old age = cracks and stretching
A test tube holder
You might try ordinary talcum powder (baby powder). It has been used to stop rubber inner tubes sticking to surfaces. The white color might not please you. You could try powdered graphite if you don't want a white coloring.
The factory situated at chennai and they manufacturing rubber products mainly automobile tyres and tubes.
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