Help with filters and what they are used for

[Sinnyone]

Hi all. New to the forum. I have had an espresso machine, Nuova Simonelli, Oscar. It has two filter holders, double and single and five filters, four of them are very large to progressively smaller. Im kind of guessing that the two bigger ones are for the double holder and two smaller are for the single, depending on how strong or how much espresso you want. I guess I will have to just kind of experiment and see what is best? there is also a fifth one that just fits into the holders but has no holes. Its smooth with no single hole like a pressurized filter. Im at a loss for what it is. Any advice on these and what the last "filter" is would be greatly appreciated. i have attached a photo for reference.
Thank you for your help.

 

[Sinnyone]

Just answered my own questions. I saw there were part numbers on the filters and looked them up. I will leave this up for anyone else that needs assistance. The filters are rated by grams of coffee beans to be used in them. Two of the filters are for the double and two for the single. One of the double is for 18g of coffee beans and the one for the single is 9g of beans. The other two had me confused because it didn't say how much coffee to use with them. They are actually used in conjunction with a Pod Kit Adapter to use pre-made espresso pods. The one with no holes is a blind filter used for back-flush allowing the machine to be cleaned. You can look up how to use it online. So, there we go. Thanks for reading.