Shimano Deore M590 9 Speed Trigger Shifters. Shimano Deore M590 9 Speed Trigger Shifters. Durable and dependable, the Deore shift levers with 2-Way release are built for the demands of off road use whilst remaining cost effective. 2-Way release allows the upper lever to still perform the same shift function, but it can now swing in either direction allowing it to be released by the thumb or index finger. A low friction design ensures easy shifting with a light and short travel.