A twin neck bottle, also known as a dosing or Bettix bottle, is a container with two chambers connected by a smaller internal tube. This design allows for the precise and controlled dispensing of concentrated liquids without needing a separate measuring cup. How a twin neck bottle works The dual-chamber design makes dosing chemicals, fertilizers, or other concentrated liquids easy and accurate. 1) Loosen the cap on the smaller, calibrated measuring chamber. 2) Squeeze the larger bottle. This action pushes the liquid from the main storage chamber up into the smaller, calibrated one. 3) Fill the measuring chamber to the desired dosage level using the measurement markings. If you overfill, simply release the squeeze to let the extra liquid drain back into the main chamber. 4) Dispense the measured dose from the calibrated chamber into your tank or container. 5) Re-cap the chamber. The smaller cap can be re-secured to prevent spills and contamination.