The Hends BL404 is one of the very slim models designed for dry flies. The hook diameter chart published by Hends allows us to compare it with other models: in size #10, its hook measures 0.48 mm, compared to 0.57 mm for the BL474 and 0.60 mm for the BL454.
The BL404 is barbless and features a Black Nickel finish. It is available in sizes #10, #12, #16, #18, and #20, in packs of 25 hooks.