On an an AR-15 with a flat top, when selecting BUIS, if you plan on mounting the front sight on the gas block, you need to pay attention to the gas block height and the front sight height. If your gas block is at the same level as the flat top, you'll need to get a front sight that is low. If your gas block is low, you'll need to get a higher one.
Anything else someone that is new to ARs should know wrt BUIS? Corrections/clarifications? Omissions/Addenda?
Also, it seems like if you do have BUIS, you absolutely need a front sight tool.
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