The std7 backbone is a big enough backbone to give a full symphonic trumpet sound with just the right amount of resistance. For anyone looking to try warburton backbones this medium size is a perfect starting point. You can then easily decide if you need a tighter back bore (numbers 1-6) or a more open model (numbers 8-12).
I love the Warburton 7 backbore. It has great response and sound, never feels stuffy, can be bright or mellow depending on your airflow and has a perfect resistance balance for all types of playing. A great backbore!!