Thinner viscosity than CDC gel, which makes it easier to apply.  
 
This Northern Game CDC Oil Fly Floatant is especially designed for CDC flies to give them better buoyancy and protection, and to help them float higher in the water for longer.  CDC feathers are very delicate and other kinds of floatant can damage these feathers.
 
To apply, simply put a drop of CDC Oil on your index finger (or direct onto the fly) and then simply rub gently and massage the oil through the CDC feather on the fly.
 
The oil comes in a handy container with a screw cap and nozzle to allow for easy application.