SL1009 iSafe"s sling backpack provides "Mobile Personal Security" for the user. In a split second, you can activate two high decibel sirens and a high intensity strobe light simultaneously to attract immediate attention to a dangerous or harmful situation (louder than most car alarms). Great security for children, teens, women, nurses, professionals, campers, hikers, seniors and more. Mono-strap school backpack has plenty of room for students on the move. Perfect for students who prefer an adjustable secured mono shoulder strap. With strap reflector and side pouch. Uses two 9V alkaline batteries, not included. iSafe"s alarm system weighs 0.5 lbs. when batteries are installed and can run up to two continuous hours before the batteries drain. Features: -Mono shoulder strap is ergonomically designed with added padding for comfort . -Large main compartment . -Air flow foam back provides extra padding for greater comfort and maximum back support. -Shoulder strap reflector provides night time visibility for additional security . -Accessible side pouch for convenient storage. Specifications -840 Ripstop nylon. -2.6 lbs (with batteries). -Designed for ages 10 and up. -Overall dimensions: 18.5" H x 12.5" W x 9" D. Operation Explanation: -iSafe Backpacks & Bags operate with two 9 volt alkaline batteries. -The alarm system can run continuously for up to two hours before the batteries must be replaced. -When the batteries are too low to effectively operate the alarm system, a red LED light will flash for 72 hours to indicated replacement of batteries. -The strobe light can be seen up to 400 yards away. -The siren signal can be heard for over a 1000 yard radius on both sides of the user.