The SE425 utilizes dual balanced armature drivers for an incredibly accurate and balanced listening experience. It includes an integrated passive crossover that ensures high and low frequencies remain distinct. The SE425 sounds very natural and is the perfect choice for audiophiles. Sound Isolating Earphones were originally developed as Personal Monitor Systems to allow musicians to hear their own performances in loud onstage environments. They work by using flexible sleeves to block up to 90 % of the background noise. You can concentrate on your music whether you are on-stage in a train on the street or working out. At the same time you can reduce the audio level to conserve your hearing. The SE535 features a durable Kevlar© reinforced cable that allows easy replacement or customisation. The formable wire ensures secure placement and over the ear configuration keeps cables out of the way. The gold plated MMCX connector has a lock-snap mechanism allowing 360 degree rotation for comfortable fit. The Fit Kit includes an assortment of foam and silicone sleeves in different sizes. A good seal is key to optimizing sound isolation and bass response as well as maximizing comfort during extended wear. Listening to music at high volumes can damage your hearing. Please listen responsibly. Turn the volume on your device down before using your ear buds or Head Phones. Gradualy increase the volume to a comfortable level.