If you don't know how to choose, you can click this page for your reference.
All models with "HE" or "WB" means it can be used with both waterborne and solvent material.
990HE , 980HE/H are higher end guns when comparing with 904HE, 881H.
903G is a special side cup mini gun best spray for difficult reachable area such as car bottom.
894H is a low CFM gun among pressure guns best use for on-site job since it's required smaller air compressor.