I'm gonna go with 9/16" diameter and 18 treads per inch, per this lookup at O'Reilly:
Dorman® AutoGrade™ - Wheel Lug Nut
Part Number: 611-127
Line: DOR
1 year limited warranty
• UPC: 19495111276
•Wheel Nut
Multiple Applications
•Black Oxide - Steel
- Thread Size: 9/16-18
•Flanged Nut - Black Oxide
- Steel
- Thread Size: 9/16-18
•Wheel Nut 9/16-18 Flanged Flat Face - 7/8 In. Hex, 1-1/16 In. Length
•Sold Individually
•Hex Size: 7/8 Inch
•Thread Size: 9/16-18 Inch
•Type: Flanged
•Seat Style: Flange
•Style: Flanged
•Thread Handing: Right Hand Thread
and Picture:
The 7/8" hex size is one of the four offered on my NAPA-brand cross-rim lug wrench. But not common enough for Harbor Fright to sell in their individual $4 English or Metric (23-mm) deep impact sockets. I was able to order a single one from Amazon, but $8.
The Jam Nuts for Dicor, as MOD noted above, would therefore be 9/16-18. THAT nut is 1-1/8, by the way. But if you have an extra piece in there, like your OP seems to say, we'd need more info to try to help with that.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB