The Bare Knuckle Pickups Old Guard Bridge Humbucker is hand wound in the UK, features Alnico II magnets and is mainly aimed at classic blues, rock, country, pop and alternative tones. From their Boot Camp range, the Old Guard pickups are in the low output range and produce an open, dynamic tone. The Bare Knuckle Boot Camp is a stripped back, no-nonsense pickup range aimed at guitar players who just want to cut to the chase and have great tone. The 50 mm pole spacing is the standard for guitars with fixed bridges (e.g. Gibson Les Paul), 53 mm spaced humbuckers (also called F-spaced or trembuckers) can be used on guitars with tremolos.