Purchased the 500ml for Home brew, have used for 2 brews now and cant get these 500ml ones to seal. Have tried everything but either the bottles or seals that come with them are dodgy. Purchased 650ml bottles as well and they seem to seal fine. Disappointed with these 500mls though, been brewing for 30yrs and decided to replace my aging Grolsch bottles with these – and havent had any success – buy the 650ml ones they seem to seal :)