The e*thirteen TRS+ dropper is a favorite on the market today. This fully mechanical dropper post with reliability, simplicity and durability as its primary design goals. This is a coil spring post with pre-set mechanical stops along it's travel range. The internally routed cable is controlled by a left, shifter-style lever that is best suited to 1x drivetrains.
This post is configured with a 31.6mm diameter, 150mm travel, 505mm overall length, 303mm max tall height, and 225mm minimum tall height.