Graco GX-7/400 Spray GunsPlural Component Mechanical Purge Guns for low to medium volume polyurea applications GX 7, GX 7 and GX 7 400 mechanical purge spray guns for dependable performance and reliability Great mixing and pattern control with its unique internal impingement mixing design Designed to handle the toughest job site condition The GX7 400 Gun is the same as a standard GX 7, but features a shorter stroke length. This is important for fast setting polyureas because