The F-400 is Fasna's "standard" jig hook. They have a standard gap and straight point much like the Hanak 400, Umpqua XC-400 and others. Despite being a 'standard' jig, relative to the Hanak 400, they run a size larger than you might expect (the F-400 sz. 18 is equivalent to the H400 sz. 16, and so forth).