There are some really nice looking kits out there that have a huge range, like .7 to 6 inch. Sure they are pricey , but what good boring head is cheap? Probably 10 years ago I invested close to 6 grand in brand new parlec finish boring heads , had heads and cartridges, extensions etc to go from .9 to 5.9 or some thing like that. I loved them, until about 3 years ago I needed to get one fixed, the adjustment screw now longer worked. Called them, and they said" yea, thats the older model, we no longer support it, but we will give you a discount on a new head, if you trade in your old one." That to me was disappointing, to say the least. I took it apart and it was an epoxy like bond that held the adjuster to the cartridge spindle that had failed. My point is, if your gonna make a large investment on a kit, probably wanna make sure they are gonna continue to service it. I still think parlec makes great stuff, just not satisfied with the way that went. If your only looking to hold a .001, you can probably get by with some of the lesser kits. Not sure if its any good but Ive often thought about this PINZBOHR BohrSTAR 210 Boring Head Triangular Insert Kit. Would love to here from someone who has used it.