18MM Downstem | Buy an 18MM Diffused Downstem for Water Pipes and Bongs - Thick Ass Glass
Clear Rigid Acrylic Pipe 18mm ID x 22mm(7/8") OD x 0.5m(20"), 2mm(3/32") Wall Round Tube - Walmart.com
Amazon.com: MECCANIXITY Acrylic Pipe Clear Rigid Round Tube 14mm(9/16") ID 18mm(0.7") OD 10" for Lamps and Lanterns, Water Cooling System 2pcs : Industrial & Scientific