The K&F step up and down rings are neat little additives to allow you to use a single set of screw thread filters with multiple SLR sized lenses. In these days of electronic post production on digital images you might be wondering why bother, well if you want to shoot say a landscape with some moving water with a slow shutter speed to blur the water, and don't want to shut down the aperture on a bright day then adding a neutral density filter will reduce the light getting to the sensor to allow your desired combo of shutter and aperture. Once you start to add to the lens that was probably supplied with your DSLR body you'll find that the don't all have the same filet size and if you bought neutral density filters for every lens size you could end up with a big collection of filters!Two sets of 9 rings are provided step up from 37mm to 82mm. (37, 49, 52, 55, 58, 62, 67, 72 and 77-82mm. There are no instructions with the rings, but it is pretty obvious once you've worked it out. Basically you screw a ring into your lens then add step up or down rings until you have a ring which is the same size as your filter. Step up rings are labelled smaller number to bigger number e.g. 37 to 49mm and step down the other way e.g. 82-77mm. The rings are all black and I happily took them out and unscrewed them, spread them out on the table, and then spent an age putting them all back together...... Not recommended! Easiest to store them stacked then your not getting dirty in the screw threads either.Ideally you buy filters for your largest/larger lens so that you mostly need step down and not up rings and vignetting does occur with a large step down such as 82mm to 55mm.N.B. The manufacturer supplied a free set of these rings and filters in return for an honest assessment review.