This is a Nodular Iron Flywheel, Perfect for that LS swap.
Application:
GM LS 1,2,3,6,& 7 with 6 bolt crank
Features:
Dual pattern mounting holes.
Made in USA 
https://www.moderndriveline.com/choosing-a-gm-flywheel/
Specifications
- Disk Diameter
- 11"
- Disk Single Or Double
- Single disk
- Balance
- Zero
- Bolt Count to Crankshaft
- 6
- Bolt Pattern
- 12-5/8" w/dowels & 10mm Pp bolts
- Bolt Size
- 10mm x 1.5mm
- Clutch Bolt Pattern
- 12-5/8" w/dowels & 10mm Pp bolts
- Material Type
- Cast Iron