I broke my bong about a year ago and just got around with buying a spare downstem. The bong is this one: http://www.alibongo.co.uk/product/frosted-leaf-sci... and it's specifics say that it's ground joint is 14.5 mm but that it's gauge is 18.8mm? Does this mean i should buy a replacement downstem in 14.5 or 18.8 mm? And what size should the downstem even be, apparently glass downstems range from 9-14 cm? I'm so confused. Help! (I usually just smoke joints or from my pipe)