An Interest Rate Collar is an instrument created to guarantee that the interest rate on the underlying liabilities rate always lies between a ceiling and a floor. It is a combination of a long position in a cap and a short position in a floor. As for Caps and Floors, we can have two different types of collars:
A "basic" Interest Rate Collar written on a short-term interbank rate (e.g. EUR Euribor 6 Months).
An Interest Rate Collar written on a CMS rate or a CMS spread (the differential between two CMS rates).