Cobalt Reel is one of the materials to craft 
Cobalt Rod in Rod Crafting table.
Recipe
You can smith reels using Anvil.
| Smithing Level | Material | Materials Required | XP for forging | Sells for |
|---|---|---|---|---|
| 66 |  Cobalt Reel |
10x Cobalt Bar 3x Threads |
150,000 | 75,000 |