The Kelford 264-EZ camshafts for the 2015-21 Subaru WRX FA20 DIT are drop-in cams to suit factory valve springs. They are a good upgrade in power across the entire rev range, keeping almost OEM response. You must retain stock rev limit if OEM springs are used. The cams can also work with the Kelford KVS87-DT valve spring and retainer set to go above the stock rev limit.