Li piston confusion

[lam1962brettagg]

Hi all
been out of the scene for a good few yrs so am a little out of touch.
been looking at new pistons for my li 150 S3 am confused that there seems to be a two ringed and three ringed piston???
the piston im replacing had two rings. is this the correct piston? (seemed to run well for 10yrs though). does it matter?
anyone suggest best make and where to get one?
got a standard Li 150 crank in it.
appreciate any help.

[ULC Soulagent]

2 ring better I’d think and SR Scooter Restoration in Notts a good place too start