Chasers also carry common travel articles and vehicle maintenance items, and sometimes first aid kits. Full sized spare tires are strongly preferable to "donut" emergency replacement tires. Power inverters (often with surged protected power strips) power devices that require AC (indoor/wall outlet) power, although some devices may be powered directly with DC (battery power) from the vehicle electric system. Water repellent products, such as Rain-X or Aquapel, are frequently applied to windshields to dispel water when driving as well as mud and small detritus, which boosts visibility and image clarity on photographs and videos shot through glass (which is particularly problematic if autofocus is on). Binoculars and sunglasses are commonly employed.