On a flat bar mountain bike the dropper lever is almost always of a thumb operated ‘gear shifter’ design on the left hand side, either mounted with or replacing the front shifter. Things aren’t quite as easy on drop bars and each manufacture uses a slightly different design. As all manufactures / posts (aside from electronic ones) use the same basic straight cable pull actuation then it’s easy to interchange and run whichever shifter you like.
Another option is utilise the Shimano GRX ST-810-LA left hand lever. This is a 1x specific lever which allows you to operate your dropper as it would a front mech. We tested this alongside the other levers in this review and found it to be the most reliable and easiest to operate by far. On the downside, unless you run a GRX compatible rear brake already, then you’ll need to make changes to your brakes and even shifting to accommodate.
We've summarised our favourite levers above. Different posts and levers run the cables different ways round (the head at either the dropper or the lever end) but additional barrels are available (and usually come with the dropper post) to allow you to cable either way round. Like everything else, if in doubt check before you buy and ask your local bike shop to do the fitting.
Thanks to Upgrade for providing us with lots of Kinesis tape to rewrap our bars during all this testing.