Sack-O-Phones is a unique storage and carry bag that doubles as a knapsack, and this one holds 5 blue Primo™ headphones with a 3.5mm plug. Each Primo™ headphone comes in its own heavy-duty, anti-lice, write-on, moisture-resistant, resealable bag. Greater focus in their lessons allow students to attain better listening skills and higher literacy. Primo™ headphones have noise-reducing ear cups that are designed to provide these benefits from the classroom, to the laboratory. The Primo™ series has a 3.5mm plug, making it a versatile unit to connect to virtually any device. It's exclusive Dura-Cord™ - the kink and chew-resistant cord, is built for every day classroom use.