VDF curable fluoroelastomers, ionically cured, having a compression set after a time of 24 h (ASTM D 39/B) at −10° C. lower than 60%, preferably lower than 50% and at −25° C. lower than 90%, preferably lower than 75%, comprising hexafluoropropene (HFP) in amounts higher than 10% by moles and one vinylether of formula: CF2═CFOCF2OCF3 (a), an amount of —COF and groups in the polymer lower than the sensitivity limit of the method using the FT-IR spectroscopy described in the present application.