Calf tail is a natural hair material used in fly tying for wings, tails, and posts. It is taken from the tail of a calf and is known for its balance of stiffness and flexibility. The fibres are straight and moderately coarse, which allows them to hold shape without collapsing in the water.

The material is commonly used in dry flies as a wing or post. Its structure helps keep the fly visible and upright. Additionally, it does not absorb excessive water, which supports buoyancy when tied correctly. This makes it suitable for patterns where stability and visibility are required.

Calf tail is also used in traditional wet flies and some streamer patterns. In these applications, it provides a clean, defined profile without excessive movement. The fibres do not flare as aggressively as bucktail, which allows more controlled tying when forming wings or tails.

The hair can be stacked or aligned depending on the pattern. When used as a wing, it can be tied upright or divided to create a split wing profile. Meanwhile, for tails, it provides a straight, durable extension that maintains its shape during use.

The material is available in natural and dyed colours. Colour consistency allows repeatable tying across multiple flies. Additionally, the fibres are easy to handle and secure with standard tying thread without excessive slippage.

Calf tail performs consistently across a range of fly sizes. It is a practical material for both traditional and modern patterns where structure, visibility, and durability are required.