Troy it's a household name - Troy Alpha Rail Free Float Modular AR Handguard

This is very nice hand guard for the price. The machining is high quality. Its extremely lite, it only weighs .620 lbs for a 13" hand guard not including the barrel nut. The inner diameter is 1.37" outer is 1.75" It does not come with a barrel nut and will attach to a standard ar-15 barrel nut. Make sure the barrel nut does not have groves on the outer housing. To be sure just order Troy standard ar-15 barrel nut listed here on Optics Planet. It comes with 3 rail attachments. Make sure you attach the rails before you mount the hand guard to your upper. The only con is having to take off the hand guard to move your rails around. It's easier this way. But the hand guard does come off easy with a few screws. hope this helps.