Runescape membership pins?

I want to ask you guys:

What is a membership pin?
How can I buy a membership pin?

I want to sell my pure for some membership pins but both me and the buyer don't know how to use them...

Any help?

 

Membership pins are 8-digit numbers that can be used to redeem one or several months of membership. They are acquired by either sending a SMS to a designated number, or calling a designated number. The fee for the pin is then docked from either your cellphone or homephone-bill.

You can either buy membership pins from sellers here on Sythe, or can call to get your own as is described above.

Buying from Sythe members is a lot cheaper, I think; though I don't know why.

 

It is cheaper. A PIN costs 15 AUSD on JaGex's site. Most of the pins come from pinlines, which are an illegal way to obtain them (not gonna say more).

I believe there's a guide on 'How to redeem a PIN' in Surround Sound's Pin Shop (it's basically dead now since he joined up with Brendan).