This is a Yankee Hill Machine Co Upper known as the YHM-15, model YHM-110.
YHM has long been a manufacturer of quality AR-15 Upper Receivers and is very proud to offer YHM A3 Upper Receivers under the YHM label.
Features:
Made from 7075-T6 aluminum (Forged)
M4 Style feed ramps and T Markings
Inside coated with dry film lube
Hardcoat Anodized matte black