Per KNS website, .154 is correct unless: A) your pin holes have worn, or B) you feel the need to have a snugger fit with a match trigger (I don't believe I would do this, BTW). In that case use .1555.
http://www.knsprecisioninc.com/mm5/merchant.mvc?Screen=PROD&Store_Code=KNS1&Product_Code=NRTHP154&Category_Code=GunParts
Sam