Hi NoHairNoFair,
Injection is not possible for lace. Lace can only be knotted. Injection is for a skin base. We offer 2 skin bases: The TL 400 and the TL 700 (New Generation base). The TL 700 is too thin to be injected. The TL 400 can be injected but you need to specify injection (no extra charge) as normally it is V looped. Some customers like the injection because of personal preference and their own hair style. With injected hair all the cuticles are going in the same direction and this can cause the hair to lye flatter.
Skin is just as undetectable to the touch as lace is. Once a skin base is attached you won't even notice it
Poly is the material that we typically put on the back and sides of lace units to provide a smooth surface to attache glue and tape. It's thicker than the thin skin used on a skin base. The TL 400 is as durable as the lace bases. The TL 700 is very thin and it tends to have a shorter life than the TL 400--that's the trade off for the thinness of the base. I have a retired customer in Arizona that wears nothing but skin---it's no problem.
Regards,
John