- Grade indicates strength level in the inch system.
- When specifying inch fastener strengths, call them out as grades.
- Property class indicates strength level in the metric system.
- When specifying metric fastener strengths, call them out as property classes. Don’t confusingly ask for a metric grade 8 hex cap screw. Ask for a metric property class 10.9 instead.
Warning: Similar numbers used for grade and property class designations don’t stand for the same strength. For example, a Grade 8 hex cap screw and a property class 8.8 hex cap screw have different tensile strengths. See table.