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How do I know if I have ISCG or ISCG-05 Tabs?

How do I know if I have ISCG or ISCG-05 Tabs?Some frames come with special tabs to mount chain guides. These are three tabs at the bottom bracket shell, and there are two common sizes - ISCG and ISCG-05. Here is a simplified diagram that will help you determine whether your bike has ISCG or ISCG-05 tabs. By far the easiest way to make a determination is to measure the distance between the two lower holes. For ISCG tabs (also know as ISCG-old and ISCG-03), these holes will measure roughly 48mm apart. For ISCG-05 the distance is roughly 56mm.

MRP also publishes a frame list, though we have not verified the accuracy.

What is the bottom bracket mount?

Some guides can mount at the bottom bracket, with the mount wedged between the bottom bracket and crankset. One example is the e13 XCX, and sample instructions for it are at

What about the E2 Type, High Direct Mount Type and Seat Tube type?

These are derailleur mounts. You will need to know which style of front derailleur your bike uses. Seat tube mounts have specific seat tube diameters that they will fit, and you'll want to make sure the product you pick supports the seat tube diameter of your bike. The sizes should be listed in the product description for chain guides that mount to the seat tube.