SteriPEN Ultra Portable Water Purifier High-contrast, user-friendly OLED display with treatment success indicator, treatment status, treatment volume, battery status 8,000-treatment lamp delivers years of purification Ultra will deliver around 50 liters of UV purification before needing to power up. Internal battery is USB-rechargeable via computer, outlet or portable solar panel Fits perfectly into store-bought bottles of water; just insert the Ultra into the bottle, flip the bottle upside down and start treating