Uses

When bought using real life currency, bonds are tradeable. Once traded to another player for an in-game sum of money or items, they become untradeable. Bonds can be made tradeable again for a payment of 10% of their Grand Exchange value (10% currently being 375,965 coins).

At any time, whether tradeable or untradeable, bonds can be redeemed for membership:

14 days for 1 bond
29 days for 2 bonds (1 day extra compared to 2 bonds separately redeemed)
45 days for 3 bonds (3 days extra compared to 3 bonds separately redeemed)

Members can use bonds for name changes as well. After the bond has been redeemed, the player can change their display name in the Option menu within the Chat sub-menu. Alternatively, a display name can also be set on the RuneScape website and under Account Settings.