Here’s what D’Addario say:
Designed for 4- or 5-string banjos and mandolins, the Banjo/Mandolin Pro Capo assures buzz-free, in tune performance at any fret. The patented micrometer adjustment mechanism allows you to dial in the exact tension needed for clear ringing notes without excessive force in any position on the neck. This greatly reduces the need to retune your instrument during and after capo use. The sleek aircraft-grade aluminum construction can withstand the toughest playing/touring schedule while adding negligible additional weight or obstruction to the instrument.