If you’ve seen bottles of Japanese soda called ramune, you’ve probably been intrigued by its novel bottle and maybe even perplexed at how to open it.

Ramune is packaged in thick glass bottles featuring a wide body and skinny pinched neck, enclosing a glass marble. Unlike a typical soda glass bottle, the bottle’s mouth is smooth-lipped, and until opened, the marble sits in it, surrounded by a gasket keeping it in place.