This air fresher creats up to 120millon / cm³ negative lons Helps to eliminate PM2.5 air pollutants, smoke, odors, dust,etc. Silent operation and easy to use No extra filter needed If you want to have a better immune system in the flu season, stop allergies from bothering you, boost your metabolism, this portable device is a reasonable option. Product Specification: Name: Air Purifier Necklace Working voltage: DC5V Power: Less than 1w Negative ion concentration: 80-120millon / cm³ Battery capacity: 250mAh Charging time:1h Working time:24-30h Weight: 30g Colour:White Material:ABS Size:4 x 7.5cm Package Contents: 1 * air purifier 1 * usb cable 1 * lanyard Only the above package content, other products are not included. Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.