1, easy to operate: the hollow cap makes it easier for the operator to pick up the needle, especially when sampling. Lids that are solid can be more difficult to handle during operation.
2. Disposal: A hollow cap makes it easier to dispose of the needle after use. If the cap is solid, then it will be more difficult to discard, and also cause some pollution to the environment.
3, to protect the user's safety: hollow cover can play a certain role in protecting the use of the process to avoid accidental stabbing. The lid is solid, accidentally stabbing fingers or other objects during operation will cause more serious injuries.