Tip Tops are measured from the Inner Diameter of the tube. 

These are Stainless Steel in Silver or Black

Sizes are 3mm, 3.5mm, 4mm, 4.5mm and 5mm ID

5mm Ring OD is 14mm, 4.5mm Ring OD is 12.5mm, 4mm Ring OD is 11.5mm, 3.5mm Ring OD is 9.5mm, 3mm Ring OD is 8.5mm