【Active Noise Cancellation】Hybrid 3 layer Active Noise Cancellation. 1. Outward-facing microphone detects external sounds and counter with equal anti-noise to reduce the environmental noise up to more than 35dB. 2. Inward-facing microphone listens inside ear canal to pick up internal sounds and produce anti-noise again to twice cancel the left noise. 3. Ear caps prevent 90% noise going to ear canal. 【Transparency Mode】 You can hear what you want to hear, which lets outside sound in so you can hear and interact with the world around you. You can clearly hear the announcement of the airline or subway and what is saying around you without taking off the headphones. 【Optical Sensors Technology】Features optical sensors technology, they sense when they’re in your ears and pause when you take them out. Adopt high-precision contact sensor, optimized for daily use and sports occasion, achieving real-time detection of wearing status. 【One-step Pairing】Pick up the two headsets from the charging case, and they will be paired automatically. Then simply enable bluetooth connection on your mobile phone to pair the device with your earbuds. 【Charge on the go】TOZO NC2 wireless earbuds can last for over 8 hours' playtime from a single charge and 32 extra hours in the compact charging case. Providing convenient charging way with no strings attached. IPX6 Waterproof can prevent from the damage of the splash by sweat and raindrops.