Badminton racquet dampener(s)

Recently saw someone with a dampener on a badminton racquet, was wondering if anyone could share their experiences using them?

Visiting the shops, I founf these two different types of dampeners available in the market.

Button type

String type

Searching the net, there was mention of simply tying a rubber band between some strings towards the bottom of the racquet frame on BadmintonCentral.