I brought this from my friend this is a jg dynamic head. I was there when he shipped the head off and when he got it back. Only used for 3 months and he decided to take another route. For some reason this does not have the jg stamp usually they do. come with retainer, dual valve spring, head been port and polish, 3 angle job and valves. Please do not talk trash on this thread or make a rude comment. I'm a man of my word and not the type to rip someone off. I'm letting this head go for $1000 obo with stock gsr cams, without cams then $925obo I do not see a serial number.