The best place to get the piston kit is Scopes and ammo.It is a mail order airgun shop based in Ontario I think.This kit will get you more power per stroke.Makes your pumps more efficient.I never put one in my 1377 because it an American model that already puts out lots of punch. .It costs 30 dollars http://scopesandammo.com/storefront/product_info.php?cPath=38_48&products_id=194
