Purchased few piece of O-ring

Purchased few pieces of O-ring near the Mine, seri kembangan, price is about few ringgit for one. 

left one in the image is made of  material Viton(Fluorocarbon) for high-temperature usage, Up to ~200 degree C. While, on the right is the normal o-ring.

O-ring is used for at a joint to prevent/minimize gas or liquid leakage. Normally you could find an o-ring at a joint, i.e. at the water/fluid tank, gas jointing cap, even at the wash machine.