USL - Upper Specification
Limit
USL, (Upper Specification Limit),
is the greatest amount in which a process or product is within the
acceptable performance limits.
This limit may be close to 3 sigma higher
than the nominal or expected mean of any process or product.
There is usually a LSL,
(Lower Specification Limit) also. A lot of products will only
have one limit. Either an upper or lower control limit. These are
sometimes called 'One Sided Specs'. A Cp
cannot be calculated for one sided specs.
