The effectiveness of the priority system stems from the fact that it is robust yet simple; only three priority colors, with a strict instruction not to try being super- accurate and pin point which among the same-colored orders should be processed first. That being said, there is one exception – a unique case where refinement of the priority system is very much needed. The case we refer to relates to situations where there are product families with considerably different production buffers. In such a situation, a product with a relatively long production buffer might have, at some work-centers, touch time which is indeed negligible relative to its own production buffer ( 1/6).