Hydraulic hoses that are used in the hydraulic system are identified based on their inner diameter, which is why their identification is known as hose ID. Identifying the hose ID is very important because, without the identification, it is impossible to find out the most suitable bosch hydraulic hose fitting. 

The inner diameter of a hydraulic hose is the gap of the empty spaces inside the cross-section of a hydraulic hose which is circular. It is very important to have a hydraulic hose with the perfect inner diameter. 

If you have a hydraulic hose whose inner diameter is more than required, then it can be the main reason behind the poor performance of the hydraulic system. On the other hand, if the inner diameter of the hose is less than the required diameter then it can result in system leakage, damage, and the pressure can also drop significantly. 

This is why it becomes very important for you to identify the exact inner diameter of a hydraulic hose otherwise; the entire hydraulic system can fail because of inner damage and leakage. So, next time when you decide to buy a hydraulic hose, make sure you know the inner diameter of that hose.