When you buy avocados, you’re often left crossing your fingers that the market has some ripe and ready-to-eat. If you find yourself with a rock-hard and unripe avocado, you’ll need to delay eating them for a few days, or you can make them ripen faster by making one more stop in the produce department.

Placing the avocado and a banana in a paper bag can quickly ripen an avocado, as the banana creates enough ethylene (the gas that triggers ripening) to speed up the process. The paper bag perfectly contains the gas while still allowing the avocado to breathe, so simply place the two fruits in a bag, fold it over to close it, and leave it on the counter.

Trapping ethylene using bananas in a paper bag will work for many fruits, such as mangos, pears, plums, and tomatoes, but as the bag will trap the fruit’s ethylene, you can leave out the banana. For some fruits, like peaches, the paper bag might trap too much moisture and ruin the fruit, so instead, use a linen napkin or clean kitchen towel.