usually lilypipes has 3 different sizes: 10mm, 13mm, 17mm (outer diameter)
and hose commonly has 3 sizes: 9/12, 12/16, 16/22 (inner/outer diameter)
lily 10mm fit with 9/12 hose (9mm inner diameter / 12mm outer diameter)
lily 13mm fit with 12/16 hose (12mm inner diameter / 16mm outer diameter)...