O ring list for FX Impact 30 caliber and Crown 25

Support[/QUOTE]http://www.fxairguns.com/support/embed/
Go to the "support" area

And after you make a list of the orings you need. This place seems like a popular place by those on the forum to get their orings.

http://www.theoringstore.com/

Here is the post on the crown:

http://www.airgunnation.com/topic/fx-crown-oring-database-parts-list/

I just look up fx impact schematic and a blower up image of the impacts shows up with all parts even o ring listed. I has to use this when I got my impact and it had not barrel o ring 
I be live it shows all sizes and what not you need to know.
and as for the parts that go bad I can't say really is think just orings.

Here is an Ebay link for a complete set of o-rings for the Impact. You select what caliber you need. https://www.ebay.com/itm/O-Ring-Kit-For-FX-Impact-Complete-Rebuild-Kit-includes-every-O-Ring-all-32/302052602782?hash=item4653bcf39e:m:mFyopJmyXuKMjRRQUhOu7TQ