Hard to find rubber grommet to glass on glass adapter. Straight 12.5mil diameter diffused downstem with 19mil male glass on glass fitting on top. Fits into rubber grommet in water pipe and allows conversion to use 19mil female glass on glass bowl, oil dome or accessories. Diffuser slots. Various lengths available. Please choose length. Comes with rubber donut grommet. Also available in 14mil. 12.5mil is approx 1/2" This is a custom made item. Be sure to order correct size. Because this item is Handmade. There may be slight variation in length. TIP: Use a little soapy water when sliding rubber grommet on to downstem. Please see Glass Accessories Measuring Guide.