This is a semi auto bolt kit for the SUOMI PK 31 and will make building one much easier. You will need to get an original parts kit (preferably with an intact trigger housing). You will also need to get our reduced ID tube (S31T-RID) and 16" barrel (S31B16) to build an ATF approved 922r compliant carbine. The instructions are detailed and well laid out. The bolt is new made and designed specifically for semi auto use and is NOT a modified full auto bolt.