Cannondale’s single-legged Lefty fork has only been available for non-Cannondales for a year, since the introduction of the LFA (Lefty For All) range. The telescopic single leg uses a keyed design and fixed tapered axle for good on-trail steering and braking stiffness at a very low weight.
The offset fork is compatible with 1.125 and 1.5in head tubes, but does require a dedicated wheel (Lefty hubs are £75). Loosening the brake to remove the wheel is a faff, and left knee clearance out of the saddle could be an issue, but you can fix punctures with the wheel in-situ.
The 88 needle bearings give a supple, ground-tracking start to the 140mm RockShox-derived air spring stroke. PBR damping is consistent and controlled with a presson, snap-off lockout/rebound adjuster below bar level. It’s pretty linear in standard form so braking dive is an occasional issue, but it can be tuned internally. Cost is high though.