Surefit 2 Tubes are like the bottom image as above, again in red or blue with a number and a letter, but also a coloured line . The Surefit 2 example is a size 1B tube. Surefit 2 Tubes have 2 ridges at the tip.
It is very important that you can see the difference between the two types of thin tube and either use Thin Tube Domes with Thin Tubes or Surefit 2 Domes with Surefit 2 Tubes, they are not interchangeable.
The size of the tube reflects its length, the higher the number the longer it is, and as a general rule the taller you are the longer the tube is likely to be.
N.B. Please order exactly what you are already using, if you want to change for any reason please ask us for advice first as o nce the item is out of the pack and it has been in your ear canal we can't accept it back for credit / exchange due to hygiene considerations. You would not appreciate if we sent one to you after it had been in someone else's ear!
If in doubt please ask our advice or alternatively the centre that supplied your hearing aids. Domes are not included and can be purchased in our 'Domes' section.