The Velo plug take the place of a rim strip. It allows improved tire seating and easier spoke repair.
These are way lighter than rim strips, the 72 plugs weigh a total of 11g. Typically a set of 24 to 28 for a wheel weighs around 4g. Having said that, these plugs are best suited to non-eyeleted rims, or single-eyelet rims, with holes ideally of 8mm dia. They arent suited to double-eyelet rims which have larger holes. Ive used them in DT-Swiss R1.1 and Sun Venus road rims. If they a little loose, I put a spot of contact adhesive under the edges of the plug to keep them secure. Being thicker and stiffer, these plugs dont cave in like some rim strips under road tire pressures. The only catch for these plugs is the rim holes have to be around 8mm and mustnt have eyelets at the surface adjacent to the inner tube to interfere with supporting the plug. So, they are really light and stiff, but dont fit all rims. If you have compatible rims, this is a good alternative to rim strips.
Does not work very well with some eyelets. I installed these on some ambrosio rims and they dont cover the eyelets completely. I developed a flat in my tube overnight without even riding the bike. After careful inspection to make sure none of the plugs fell out I put in another new tube - all seemed well initially but again by morning I had a flat. I think these plugs would likely work well with non-eyeletted rims but they simply dont cover the seams of eyelets completely - I will be returning to the heavier but reliable Velox.