The real sour diesel is clone only. But after about 5 releases of different versions along the breeding line, I have heard that rez's IBL is very stable and as close to the clone as anything around. I've grown the clone since '06, at that time rez's seeds were terrible. He received the clone in like '04 and by '05 he had seeds released.. Some friend's grew some. Way different growth structure. Not the thick chemy sour nuggets. Recently other SD from seed I've seen has been much closer to the original clone.