The Pro-Series 18.8 sets are high-strength studs made in Germany.

A special steel is used which has a tensile strength of 1850 N/mm² after tempering.

All threads are formed and not cut as commercially available. The so-called "rolling" of threads increases the strength of the tooth flanks by approximately 30%.

All Pro-Series products are supplied with a nickel coating and are therefore protected against long-term corrosion even under the toughest conditions.

A big advantage of Pro-Series over other manufacturers are the nuts and washers included in the set as these also have a tensile strength of 1850 N/mm².

With this kit the oem cylinder head screws are replaced by high-strength Pro-Series 18.8 studs.

This is necessary for high performance applications were the oem cylinder head bolts can "lengthen" during operation and the cylinder head can "lift off".

With a tensile strength of 1850 N/mm² the Pro-Series 18.8 studs provide an improovement.

Furthermore, these studs do not have to be replaced after dismantling but can still be used.

These are the equivalent of ARP Custom Age 625+

Very strong and not comparable to the black ARP standard bolts/studs.

4-cylinder engines have been run with over 1300hp (4.6bar boost) and V6 (Nissan) with over 3000hp with these products without any problems.