I use spoke prep on wheels that are built using rims with eyelets like a Mavic open pro, If the rim is not eyeleted I don't use it because the nipples bind up with the rim as the wheel is tensioned. I build many wheels and never have a problem with any of them. If you ar eusing an eyeleted rim and don't use spoke prep the spokes can come loose as the rim is being ridden. other companies make a similar product, DT has one and Mavic also.