Belkin Behind-the-Head Earbud Headphones 3.5mm Jack with 2.5mm Adapter for $2.65 shipped after coupon code CS10. Here is a screenshot for your reference. This headphone features a 4-foot long cable with a 3.5 mm jack, and a 3.5 mm to 2.5 mm adapter so it can be used on a cell phone or PDA.