MPO adapters follow TIA/EIA-568-C.3 and TIA-604-5-D polarity standards,MPO adapters available in Type A Polarity: Black adapter housing with key-up to and key-down configuration; K=1 and Type B Polarity: Charcoal gray adapter housing with key-up to key-up configuration; K=2, MPO adapters offer a compact design for ultimate density for full dimensional details. See TIA/EIA-604-3 for full dimensional details