"Cross Flow Fan" computing products and L10 life expectancy MTTF of: product life expectancy MTTF refers to the expected time of the product occurs when poor 63.2%, or 36.8% of the time said product reliability life expectancy L10 is the product of 10% occurred when bad the expected time, or 90 percent of the time called reliability. Please not that bad of a certain definition of the specification, such as: (1) you can use a number of products for testing by 2000,3000,5000,10000,18000 hours after the test the speed of their current consumption exceeds the specifications defined as poor . (2) or to measure how much precision measuring instruments define the axis of bad residual amount left to feed lubricating oil.