This is the ProTek R/C Carbon Fiber Soldering Jig. The jig features a rectangular 17x10mm slot that securely fits Deans/T-Style and XT60 sized connectors, as well as two 8mm holes to fit the bullet connector of your choice. If you just need to solder or tin wires, the vertical posts open up to 10mm providing plenty of space for a variety of wire AWG's. To keep the jig planted, four rubber feet on the bottom keep it from moving around while you work.