Belleville Spring Washers maintain bolt preload by preventing bolt tension loss.
They are mainly useed in area where differential thermal expansion, embedment relaxation, vibration, relaxation and bolt creep 
and bolt yield are problematic.
Belleville Springs on your bolted connections can reduce risk of failure, downtime and maintenance costs. 
Bolt size are different for different material.
Details as below:
1.material of 1074 carbon steel
  bolt size in imperial are 3/8inch, 1/2inch,5/8inch,3/4inch
2.material of 17-7 PH stainless steel
  bolt size in imperial are #6, #8,#10,1/4inch, 5/16inch, 3/8inch,7/16inch, 1/2inch,9/16inch,5/8inch,3/4inch,7/8inch, 1inch,1 1/8inch, 1 1/4inch,
  1 3/8inch,1 1/2inch,1 3/4inch, 2 inch
3.material of 301 stainless steel
  bolt size from #8 to 3/4inch
4.material of AISI6150 alloy steel
  bolt size range from #10 to 1 3/4inch
5.material of Inconel 718
  bolt size range from #6 to 2 1/2inch
We also produce belleville spring of other material.
For more details,pls contact us.