Landing leg extensions create no significant additional drag, so flight performance is really not affected unless maybe you are in sport mode doing 50mph, best to take them off before trying to break the sound barrier.
The upsides are getting your Mavic off the ground a little bit more thus giving the gimbal a little more breathing room in case of a hard landing. They also raise the belly of the Mavic off the ground to give the belly exhaust better air flow. They also protect the 2 rubber feet of the Mavic which are hard to find aftermarket and not available OEM.
The downside is having to remove them if you are using the OEM box to tote your Mavic around. But they come off in a snap, and can you can stick them where the micro usb wires are in the case.
I sell them $14.99 shipped USA Paypal. I currently sell 2 colors, standard Mavic gray and golden colored, if you have a different color skin to match it.
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