Nordyne orifice #54. Also known as drill size 0.0550.
Hex head is 7/16", length is 7/16", threads are 1/8-27 NPT.
Picture is for reference only. Hole size will vary on actual item.
Replaces Nordyne part # 660794 & 661054.
Will also replace Rheem part # 62-22175-54 & 622217554 although the length of this orifice is a touch shorter.