This is a replacement 6 inch magnetic test tube for our Floating Propagator only. Diameter of the test tube is 1 inch/25mm. Please check out our Propagator at: https://www.etsy.com/OfficialTakenoko/listing/880502649/floating-propagation-station-magnetic?utm_source=Copy&utm_medium=ListingManager&utm_campaign=Share&utm_term=so.lmsm&share_time=1627009062036 6 Inch Magnetic Replacement Test Tube For Floating Propagation Station, Window Planter, Cabinet Save Space, Fridge Magnet