I purchased one of these as the website said it 'takes most standard glass jam jars'. I have tried every size jar I own and none fit properly. & I make jam so I have a lot of jars! Shouldn't it be a tight fit? Plus, when I fill it and turn it the right way up, the tray fills with the entire contents of the (big) jar making the jar a bit pointless. The middle bit with a hole in it is removable. I know I could've just bought a plastic one for cheaper but I thought this would be good as I could see the water level, and I try to avoid plastics... What am I missing here? I can't return it & I want it to work!