Reliability is the ability of a part or product to perform as intended (i.e., without failure and within specified performance limits) for a specified time, in its life cycle application environment. Reliability specification and demonstration is an activity between customers and suppliers. Because high IC reliability is an inherent quality that is partly derived not only from the soundness of the IC chip's design, but also from the degree of process control and cleanliness and the integrity of the IC-chip package and interconnections, failures tend to be lot-related. So, although a good reliability track record for one vendor's IC type means a reasonable probability that the vendor's next shipped lot of the same IC type will have the same high-reliability characteristics; there is no guarantee that such a lot will not exhibit abnormally high failure rates -and such things do happen, causing IC users to be constantly on the watch.