I heard back from Western Pacific Trading the makers of GTU and WL Gore as well.

GTU is NOT the same as Gore GFO. GTU is graphite impregnated PTFE packing braided with some Gore fibers. It does not meet the 100% Gore classification and is different from GFO.

To be GFO packing the braiding has to say 100% Gore stamped directly on it.

Here's what WL Gore has to say on the knock offs:

"Different Fibers can cause Major Problems -

Some users have tried “trading off” GFO® packing performance for lower price. However, low-price competitive “look-alike” black PTFE fiber packings perform differently.

Recently, some look-alike products have targeted one performance criteria – thermal conductivity – suggesting that this attribute makes them “equivalent” to GFO® packings. Close inspection of some competitive products show that these products consist of pure PTFE with a thermally conductive layer. The design is much like a wire: a thermally conductive interior surrounded by an insulator.

Pull on these fibers and they will turn white. The material in contact with the rotating shaft is pure PTFE, known for its thermal expansion and shaft scoring behavior at higher service temperatures. This outer PTFE layer of the look-alikes also raises questions about how efficiently this packing is able to provide lubrication during break-in and service of the packing."

My experience has only been with real Gore GFO and the stuff is really, really good. I would think GTU would perform better than flax packing but not as well as real GFO...

Hope this helps clear thing sup..