With competition-level LiPo batteries mostly available with either 4mm or 5mm plugs, mix and matching different brands with various sizes plugs may be a real challenge. Arrowmax had come to the rescue by launching a 5mm to 4mm down-sizing jacket. Different with other comparable services and products available on the market now, the jacket functions inserting into the 5mm plug on the LiPo and effortlessly transforming it to 4mm. No soldering and extremely convenient to maneuver from pack to pack. You'll sustain your asking cable and ESC experience of the same 4mm plugs and still having the ability to make use of LiPo with 5mm conncetion. They come 24K gold plated for maximum conductivity.