A traditional fly reel had a very narrow central circumference. Meaning the hub of the reel was small. This allowed you to get a lot more line on the reel in relation to its overall diameter. While offering relatively large line carrying capacity, this design had its draw backs, as follows.

• Low retrieve speed
• Line coils/loops

The low retrieve speed is due to the small size of the hub. One turn of the reel handle will give you only one turn on the reel hub and if the hub is small it could only gain you a matter of a few centimetres. The narrow hub also tended to cause the line to coil in narrow loops, which would effect casting and fly presentation.

A large Arbor reel has a large hub. You get less capacity compared to overall reel size but it negates the tight coils causing the line to twist and loop. You also get a faster retrieve, expending less effort to wind in. The other added advantage is it allows fish to take line more smoothly when on a run, preventing breakages in the leader if you are playing against the reel or caught unawares.