Conditioning and strength--endurance. 
The bold, new way to train, Zenith is designed for strong and healthy hands in the 21st century.
Zenith Trainer:  If you do your work sets with a Captains of Crush Trainer, this is where we recommend you begin with Zenith grippers.  It will be easier to close than a CoC Trainer, and that's by design.
 No. 1475 (1 lb.)   Zenith Trainer  $39.95