Getting the pool started for the season can be a task that drives one crazy. All those tiny parts that seem to have just disappeared over the long cold winter. One of the biggest headaches are o-rings. When you find that you are missing o-rings, the best way to get that o-ring replaced is to know what it fits. A name or model number is preferred when you come into the store, but don't fret, there are other ways to find what size o-ring you need.
Just take a piece of paper and place it over the "track" where the o-ring sits. Holding it in place, take your finger and push on the paper making an indent of the "track". Bring this paper to the store and from there, we should be able to use our handy dandy o-ring chart to match up what o-ring you need.
After you get the new o-ring, and if it fits, take the number and e-mail that it to yourself with the subject "Pool Parts". This way, whenever you need that o-ring, you have the number out there in cyber-space.