I have been using Gamma copolymer line now for past two seasons and am more than satisfied with it. I used P-line CXX for years prior and it is a good line also...but the Gamma does not get as much memory nor it is as stiff as the P-line...actually works very well on my spinning rods too which is something that P-line did not do. Mono is just what it means..line made from a single polymer...copolymer is made of two or more polymers...there is a definite difference in the two types of line in stretch, line strength and abrasive properties.