The Hamilton Buhl SOP-HA2V Sack-O-Phones- 10 Pack of Hamilton HA2V Personal Headphones with Foam Ear Cushions and Volume. Sack-O-Phones packaging is a unique bag that doubles as a knap sack and holds 5 deluxe or 10 personal headphones. It's a great way to store headphones easily and economically, no need for costly plastic cases for storage.