These are stainless steel bubble stones, which last a lifetime, wear-resistant, and they do not give off to the water or other liquids. The plastic of the tubes in the water is also foodgrade, and the blue caps are very sturdy and durable. The hoses in the blue caps are fixed with a compression fitting, if you want to loosen them, push the gray ring down and pull the hose out of the cap. It’s just as easy to push the hose back into the cap. The white tube is attached according to the same system, but a lot firmer. You can connect the nasal cannula to this.