I bought this kit primarily for the extension hose. My MK2 is very close to my CPAP machine so I don't currently need the sensor extension. You NEED this hose and the cleaning brush! I have had so many issues with the hose getting kinked and restricting water flow. This hose is reinforced right where you need it to be at the ends. Plus, the extra length makes it so much better to place your equipment wherever you want without worrying about everything reaching.
I had a terrible bacterial bloom in my MK2, the hose, and the CPAP reservoir. A mosquito was drawn to the UV light and died in the water chamber of my MK2. I assume this is what caused the bacterial bloom. It was a nightmare. Everything was easy to clean - except the hose. Ugh! I was blasting the hose with CPAP cleaner tablets, soapy water soaks, but the final cure was blasting OxiClean through it (DO NOT DO THIS). I know this damages silicone due to the oxidation, but I was desperate. Now that I have the cleaning brush in this kit, I can clean it properly with just soapy water and not worry about degrading the silicone hose.
Overall, I highly recommend this kit. It is a great addition to your MK2/MK3 setup.
