I live on the road retired to my travel trailer. I like to keep extra parts for most important items so when I ordered my trelino I ordered these inexpensive items just to be prepared.
Works as it's intended. I do however wish Trelino offered all the products to USA customers as they do to their European market.
Living full time in my Campervan requires me to be ready with all my Trellino products. 2 Membranes can last me more than 2 months. Can’t live without them.
I think it's always a good idea to have a spare one of these just in case one is accidentally thrown out when emptying your jug.