Filters, endlessly useful but staggeringly expensive, especially if you insist on the very best, such as this gorgeous 58mm Skylight example from Kenko.
Refreshingly, Kenko chose to describe this one as simply a Skylight filter, rather than with some arcane code, so no doubt as to what we are dealing with!
The filter is in excellent condition, with very few signs of use at all that I can make out. Built with the familiar Kenko heftiness, it is ready for you to get to work immediately!