While most Banjos have flat fretboards some have a radius like a guitar.  We have you covered either way, because every Thalia Capo includes both rubber and teflon fretpads with no radii (flat) and a range of fretpads with radii for use on Banjos that have a radiused fretboard.  Our standard fretpads work just fine on most Banjos that we have tried, but if your banjo has a thin neck or a compound radius fretboard, then we would recommend using our XL fretpads.