The O-Ring is a blue, rubber ring which is used to provide an airtight seal between connected parts, such as between the diffusion tube and filter cap. If the part is broken due to general wear/fatigue, there will be a leak and it should be replaced. Refer to your make, model and diagrams to ensure this is the best part for you.
The Manifold Filter Support (Tube, Diffusion) is a black, plastic part which is used to secure the filter. It attaches with the filter mesh and the filter cap. If broken, damaged, or worn it should be replaced. Installation is rated as "Easy" by customers. Refer to your make, model and diagram to ensure this is the correct part for you.