Got the ball carp cap today from dhgate and it's not that good for oil. It doesn't seal enough. Ad originally said it was 50mm but now it says 28mm. I can tell it's not 50mm. That size might work better but I'm not sure rounded glass and the liger ti are going to ever seal nice. However it's really nice for full melt. The ball helps collect the vapor and I've been able to get better hits than I was. So @herbivore21 you might like it. Time to get a storm cell cap.