Extra Length Vent Drills are designed for drilling vent holes in rubber tire molds and for drilling very small diameter deep holes in metal. They are sometimes referred to as Small Diameter Long Boy Drills.
Vent Drills page 107

SIZE DECIMAL EQUIVALENT FLUTE LENGTH OVERALL LENGTH
1/16 .0625 2-1/2 3-1/2
1/16 .0625 3 4
1/16 .0625 3 5
1/16 .0625 4 6
3/64 .0469 2 3
50 .0700 3 4
50 .0700 3 5
50 .0700 4 6
52 .0635 4 5
54 .0550 4 6
55 .0520 2-1/4 3
55 .0520 2-1/2 4-1/2
55 .0520 3 4
55 .0520 3-1/2 6-1/4
57 .0430 2 3
57 .0430 3 4
57 .0430 4 6
58 .0420 3 4
60 .0400 3 4
60 .0400 4 6
68 .0320 2 6
69 .0292 2 3
73 .0240 5/8 1-1/2
74 .0225 1 2