This are usally small and “cheap” parts, like day discs, and are posted in a Jiffy envelope without tracking (shipping = € 2,50)!
Due to new EU-rules, I may not ship parts as a normal letter with stamps but I have to send them as a “package” with a bar code: I have to enter all details of the contents and the shipping address into the PostNL website and generate an address label (so they can find me if there are illegal substances in the envelope). Stupid enough, this bar code cannot be used for tracking the package, only for finding the sender.
This “package” needs to be delivered to the mail in a special bag so it is processed correctly. If I just put it in the mailbox, they cannot properly weigh the package and I get billed for 100+ grams).
This applies to all small items that I am sending, so usually once a week I give the bag with “packages” to the postal services.

These new EU rules are making business harder, but may result in a safer world?

I am using standard post, because Dutch tariffs for registered mail are ridiculous (€12,55 for EUR1, €14,55 for EUR2 and €19,30 for rest of the world). If you insist on registered mail, tell me in the comment and I will make a separate invoice for the price difference.