This support can be put on the list of best neck supports when working on your guitar.
It will keep your guitar in place and it does not let your neck slide towards either side (up/down/forward/backward/sideways).
it has a concaved side and a flat side when you want to work on the back of your guitar.
The main downside is that when you lift up your guitar, the support will flip to the flat side more than once, so the neck rest does not stay in place when there is no guitar on it.
Another minor downside is that when leaving your guitar (tested with 3 guitars 2 of them with lacqued necks and one without) for a longer time (overnight) it tends to "stick" to the rubber foam but does not leave any mark, it just sticks a bit.
pros : keeps your guitar in place when working on it and has a flat side aswell
cons : neck rest rotates to flat side when not in use and tends to "stick" on the neck after some time