These are Special designed drivers for Bose Series Headphones. it delivers much more better sound quality than its Originals. We are professional speaker driver factory,in order to beat Bose original drivers, our professional engineers tested over 300 times with QC15,QC25 Headphones.You will enjoy your music with our drivers. like my brand, elfinear. *Note* Item sold by PairsModel :QC PRO To provide clear cristal mylar paper for the unique driver unit,Mylar Cone Paper materials are imported from Japan and which is made with precise single layer mold by Taiwan Manufacturer.You can see the difference with other drivers directly,what's more, the carefully pressed or transformed cone can return itself to normal after 2 or 3 hours,do not like a most of easy demaged Mylar paper. This feature is very important to a high quality speaker driver. As usual, we keep our style to provide strong magnetical magnet to ensure the speaker driver powerful enough.Warm,Strong Bass style like BOSE drivers,the frequency is wide ,we can hear more instruments play than normal does. Parameters: Mode: QC Pro Type: Dynamic Use:HiFi Headphones Construction: Coaxial composite Magnetic circuit form: Internal magnetic formula Frequency: full range Rated power: 20mW Impedance:25 ohm Frequency: 20-20KHZ Directivity: the marked color point is the unit positive pole Sensitivity: 125dB at1KHz Distortion: 1 TMD% Packaging: 2* Headphone Speaker unit Instructions: Please test the speakers with a multimeter before soldering. The colored spot is for positive pole +, the other side is for negative -. Soldering with less than 3 seconds. Otherwise, the voice coil or circuit board can be burned out easily.