I put a LaRue 9.0 on my CAR length system so the gas block would be covered. I thought it looked cleaner. Was very easy to take the sight tower off and replace with a LaRue Gas Block which I needed because nothing else would fit under it. I like the LaRue HG's so much I put a 7.0 on my 7.5" SBR. It is easy to do the work your self if you have the tools and only took me about 45 minutes to complete. If you have a mid length system why not get a 12.0 and cover the gas block?
I have purchased all my LaRue items directly from LaRue. The prices are the same as any of the dealers and you will know if the item is in stock when you talk to them. Shipping is two to three days by Priority Mail and only $5 per order, and every order I have placed came with a bunch of freebees (2 LaRue Survival Tools and 2 Hats) with every order.
The 9.0 is obviously the one on the bottom,
MadDog