how to buy pocket knives for blade material?

buy pocket knives,we need to know some of characteristic
 
 Blade MaterialsA good blade combines good edge retention, ease of re-sharpening and rust resistance.·         S30V is the best blade steel available. It is a high vanadium stainless steel with even higher edge retention.
·         154CM and BG-42 are two custom steels with much higher carbon content, giving them higher hardness ratings and dramatically higher edge retention.
·         420HC is a stainless steel that provides excellent rust resistance, is easy to re-sharpen and has good edge retention.