Use the John Guest Quick Connect (QC) 2-Way Splitter 1/4 inch splitter for multiple reservoirs when using the Stealth RO™ system or the Small Boy™ system as well as any other system that takes 1/4 inch tubing. Use the 3/8 splitter for multiple reservoirs when using the TallBoy™ system as well as any other system that takes 3/8 in tubing.