this is true, it will make sex longer, but... have used one of these myself d i find that they are rather uncomfy t this is because they cut of the blood to your penis so it cant go soft. i would defiantly advise a rubber 'cock ring' as these are more stretchy and they are also more comfy to were. i really hope that this helps you. :)
It will not be available in Sri Lanka due to the non-marketing of sex toys, not many people would consider it! valuable to sale in Sri Lanka. You can get it online stores e.g. Amazon. I would not suggest that it will be a good idea to use it, it might cause damage to the penis, you can try sex herbal pills.