Can't remember the gauge (maybe 130) , but I used a Chromes B string. It was bright and clear. It was a big stiff muther, and sounded great on my 34" scale G & L fiver. If there's ever a commercial market for F#, C#, G# flats
...anyway somebody somewhere will be willing to custom make them. In the upright bass realm, a Thomastik Spirocore Stark B (flatwound steel) is a huge string.