What is the best way to send Nintendo Gameboy Advance games?

Today I sold some modules and I want to pack them tomorrow morning and send them directly. I wonder how should I pack it? You probably know these little modules for the Gameboy Advanced SP. They would easily fit in a letter, but is it also appropriate to send these games in letters? I don't want to pack a package for every single module. It is also much more expensive. What alternatives are there or what would you recommend?

Letters with air cushions, in the German language there's certainly a technical term for this.

You could send it by registered mail

Bubble bags are called

Just take a padded envelope (bubble envelopes) and send the games with it. Then they are well protected and shipping is not too expensive.

You can get them directly in the post office and the price shouldn't be much more expensive than a normal letter, but much cheaper than a package.

But for security as a registered mail it is insured.