There’s no shortage of portable speakers on the market. But it’s hard to find ones that aren’t bulky or battery-draining. Designers Lin Nien-An and Cheng Ya-Fang have found the answer, creating the funnel-inspired Green’s Voice Speaker System, that turns any empty plastic bottle into a party. It’s the perfect picnic accessory this fall.

Just screw the rubber cradle onto the top of a used bottle. The speaker creates a beautiful low-tech sound, using the bottle as an enclosure to amplify the sound. The Green speakers are made from an environmentally friendly, biodegradable plastic, and the long-life battery lasts 10 times that of an average lithium battery. These smart speakers give a whole new meaning to music on-the-go. Keep them on hand, and you’ll be prepared for any spontaneous party that comes your way.