The different models are going are going to vary by Gen 2 (NL1,NL2,Ect.) vs. Gen 3 (3AL1,3AL2,Ect.), as well as different tube quality broken down into three levels. Level 1-3, level one being the cleanest of the three. For more detailed information and breakdown, please feel free to reach out to info@agmglobalvision.com.