The 40-Series studs are designed to be used with a metal grommet ( sold separately) large and small diameter grommet are available separate.
The dash number is normally stamped on the head of the stud. The dash number corresponds to overall stud length using the following formulae:
Dash number = (Length - 0.62) / 0.03
Length = (Dash number * 0.03) + 0.62