The 'K' (405) are shorter than the 'F' (410) and of a slightly different profile. If you are running pods, the K ones will work on a F, although it's a bit of a wrestle getting them on. If you have standard airbox setup and use the K's, you will create a larger gap between carb and airbox. I have used K's on an F2 with pods but don't have experience of them with the standard set-up. Maybe if you used them you may be able to adapt the rubbers airbox-side as a leak this side of the carbs is not as critical?