This is the rubber O-Ring which you may need, if you replace the battery in your Core Watch, in order to keep it waterproof. It comes with a set of instructions.
Unfortunately these are now sold separately to the battery to shipping issues from Suunto.
When you purchase this product you will be offered the CR2032 battery for the Core watch.
Customer Reviews of Suunto Core / Essential Service Kit
Had a problem with sunnto all black steaming up in the face.
Ordered new O ring.... easy fit, problem solved!!!
Overall it’s an expensive price for a seal but it is the cheapest on the market.would be great if it included a battery but you can’t have everything. Overall Great service, fast delivery..... recommended!!