The Cocoon sleeping bag liner sold at REI is always too narrow for me, and I keep tearing it to shreds. I got tired of replacing a $60 piece of gear, so I bought my own silk which is a pretty orange and can be used for an emergency attraction device.
Using the orange silk made my own wider silk bag liner. It is open on one side eliminating stress points which caused tearing of the Cocoon brand.
It is a good thing I had sewing class in middle school.