Every Deer has various deer hair on their body that is different from the other hair, each has a specific use in fly tying.
Mask: short deer hair. medium texture, best as part of deer hair dubbing.
Back & Neck: fairly long, with fine texture, great for wings, not as buoyant as rump and belly hair.
Flanks: medium length, course/medium texture, best for spinning on small hook patterns, surface fly patterns
Rump &Belly: long course hair, best for spinning large bass bugs requiring buoyancy. Belly Hair is best for dying bright colors, since the deer belly hair is white.
Legs: short fine textured, best for small hook patterns, less buoyant.
http://globalflyfisher.com/staff/hel...ing/chart.html
Bucktail: tips least hollow and less buoyant, best used on streamer patterns, that are for below surface presentation. Most commercial Bucktail is from the White Tail Deer, that has a edging of white and the center is brown, the edges are take a good color from dying, the central portion is shorter hairs and the dying colors are muddled.