Here is Hans:
http://globalflyfisher.com/tiebetter/tying-with-cdc/
In my experience, puffs do not float as well as the CDC feather. I primarily use them for patterns I fish sub-surface like an RS2. In any case, if there is a desire to use puffs, use more than one. Rene Harrop once remarked that most tiers do not use enough CDC when tying patterns that incorporate CDC feathers...
JUJU (UV 2) RS-2 EMERGER (Baetis, Gray/Olive)
PT/TB