ATTENTION:  If the measurement of your lens falls in between two sizes, please select the next size up.  For example, if your lens measures 65.5 (size S), please select size 66-69 gear (Size M).  Before you invest in parts to modify your lens, we strongly encourage you to invest in the tools needed for proper measurement.  A digital calliper sells for $10 on Amazon.com.  Please consider purchasing one.