CERTIFICATION: We offer solid rivets in 1/4LB packages which are uncertified, and in 1LB packages that are certified. The difference is simply that the 1LB package (whose part number ends in "C") is guaranteed to preserve the manufacturer's LOT numbers; whereas the 1/4LB package may contain a mixture of 2 or more lot numbers and is therefore untraceable. Whether or not you need "certified" rivets usually depends on the nature of the job. Generally speaking, repairs do not require traceable rivets, but definitely consider using them when consistency is required for major sheet metal fabrications or repairs. It's also a good idea write down the manufacturer and LOT number in your maintenance logs for future reference.