Seachem Bottle Adapter Plugs come in two sizes and allow you to seamlessly connect dosing pump tubing to any Seachem or aquavitro® bottles ranging from50 mL–1 L and many other common supplement bottles (24 mm–28 mm) on the market. They are ideal for use with aquavitro® sentia™ dose and doser tubing. Fits tubing sizes up to OD 0.192 inches/4.88 mm. Bottle Adapters Sm: 50 mL–500 mL (24 mm) Bottle Adapters Md: One liter (28 mm) Sold in packs of 6. Tubing sold separately