Hi there I need to order new left complete piston for my GS. According to manual and realoem, there are only one size category currently, marked as AB (AntiBluesmoke ). But there are two weight categories - "+" and "-" :huh 11 25 7 652 663 PISTON, ANTI-BLUESMOKE - AB+584-594GR 11 25 7 652 664 PISTON, ANTI-BLUESMOKE - AB-574-584GR My old complete piston weights 585.3g, so it seems it is "+" weight category. What does circled mark mean? Does it mean weight category? Under circle, there is "101L37" mark (maybe piston diameter and height) Thanks.