I bought an Aero Precision M5 upper a few months ago. I have since decided to go a different route. This is an AR10 upper receiver. I was planning on building a 6mm creedmoor rifle. This receiver can be used for any AR10 caliber. So 243 Winchester, .260 Remington, .308 Winchester, .338 Federal, .358 Winchester, 6.5 Creedmoor, 7mm-08 Remington, and many other. It is the enhanced version so it comes with an integral barrel nut and mount. You can still use any AR10 barrel from any manufacturer. I bought this brand new from Aero Precision. Im asking $150.00 for it.   I included a picture of what I paid for it brand new. You can text/call me with any questions. 785-820-0260