 The sole reliance of the NFL on NOCSAE certification, without considering the tested safety results and other data on helmet models, has been criticized by the players' union.Critics note that while NOCSAE standards call for equipment to be reconditioned, where possible, and recertified every year, a school may keep its helmets as NOCSAE-certified simply by never submitting them for re-certification.The inflexible nature of NOCSAE guidelines, stemming from the hesitance of helmet manufacturers to take any risks that could lead to lawsuits, leads some to argue that innovative helmet designs may be underdeveloped.