These are stretch bolts and must be replaced every strip down (5 required).
These fit /6 models up to the following engine numbers;

• R60/6 up to 2921619 (01/1975)
• R75/6 up to 4020451 (10/1974)
• R90/6 up to 4050185 (09/1974)
• R90S  up to 4080436 (09/1974)

and for USA models;

• R60/6 USA up to 4920661 (01/1975)
• R75/6 USA up to 4940405 (10/1974)
• R90/6 USA up to 4960789 (09/1974)
• R90S USA  up to 4980303 (09/1974)

For models with later engine numbers, please see ENA62060