This is for the Schnuerle ported .40
This piston uses a Dykes Type ring and no
There is also a piston that does not carry the "s" in the part number. At this time we believe the only difference is snap ring grooves to retain the wrist pin. These were marked with the "s" from WEBRA in Austria and have the groove but we are not sure which is suppose to have the groove.
Please identify which version you want when ordering.