My opinions on FAQ for G scale
Track-
Rail sizes 0.350 (LGB, USA, Aristo[ brass,stainless steel)
0.250 (Llagas Creek, Sunset Valley RR [aluminum, nickel silver)
0.215 (Same as above)
0.195? I've heard of it but have never seen it.
I personally use code 250 aluminum rail from Llagas...