Manitou Jack Dropper Post - 31.6mm 160mmManitou Jack Dropper Post 31. 6mm 160mm. The Jack dropper post is available in three drop options 185mm 160mm and 80mm for improved handling when you need it. Available in 30. 9 and 31. 6mm diameters the Jack includes a Manitou under bar lever which features a cartridge bearing for smooth precise operation. To further the smooth operation and setup on the 185mm and 160mm post the included 1. 1mm cable with Manitou specific cable head negates the use