30 Pack headphones bulk with 3.5 mm plug These bulk headphones designed with adjustable headband, comfort and lightness,ideal for classroom use and school testing. These headphones bulk with 3.5 mm plug and 4ft cord works with smartphones, chromebooks, tablets, laptops, computers, fitness and audio equipment. These class set headphones can be widely applied for classrooms, school, libraries, museums, hotels, gyms and more places.