Elecraft found significant performance improvements due to using crystals with much more closely matched characteristics. Newer kits, like your, come with the crystals. Upgrade kits were made available to those with older K2's. Ron AC7AC K2 # 1289 -----Original Message----- I'm still building K2 3453. Why are people getting new crystals? 73, Tom, W6WW K2 #3453