Unless that's a 'proper' Gravity Dropper post it looks very similar to my cheapo Tmars dropper that cost about £45 (http://www.ebay.co.uk/itm/161172390535) and has three heights, 110mm down, 55mm down and up and is cable actuated with a simple pin that's released by the lever and seems to work just fine. The lever they come with is a fairly clumsy big omnidirection thing that feels anything but positive so I used a Suntour fork lockout unit that I didn't need to replace it which gives a far nicer feel and is nice and minimalist on the bars. Similar procedure shown here: http://goatshell.blogspot.co.uk/2014/03/origin8-tmars-dropper-seatpost-1st_3.html though I've used a little barrel lock thing with grub screws to finish the cable (possibly from an old Magura HS33 mounting kit?) which is nicer than the ugly solution that dude's used.