The International Standard Chain Guide (ISCG) mounting system was developed by a number of companies to achieve a consistency across the frame manufacturing board in 2003.

While the original ISCG standard worked for a number of years, current frame manufacturing and component designs now demand a more rigorous standard.

As a result the newer ISCG’05 standard was developed by drivetrain component and frame manufacturers to accommodate the need for more strict guidelines and better compatibility.

This means there are now two ISCG standards

The original ISCG standard also known as ISCG03, ISCGold or simply ISCG

The newer ISCG standard known as ISCG05

Not sure which ISCG standard your frame has? Simply measure the two lower bolt holes and compare them to the diagrams.