Material:    Tantalum ring
Temper condition: annealed
Specs   :    acc. to ASTM B 365 - 98 R05200.
Chemical composition: 
                O                   0.0150   %max
                C                   0.0100   %max
                N                   0.0100   %max
                H                   0.0015   %max
                Fe                  0.0100   %max
                Ti                   0.0100   %max
                Ni                   0.0100   %max
                Si                   0.0050   %max
                Mo                 0.0200   %max
                W                  0.0500   %max
                Nb                 0.1000   %max
                Ta                 Remainder
Size :   38-300mm Outside Diameter x 28-280mm Inside Diameter x 1-20mm thickness.

Typical Sizes :
43.7mm OD x 28.6mm ID x 35mm thick
51.6mm OD x 36.5mm ID x 35mm thick
92.9mm OD x 69.8mm ID x 35mm thick
127.8mm OD x 98.4mm ID x 35mm thick
153mm OD x  138 mm ID  x 41mm thick
158mm OD x 123.8mm ID x 35mm thick

Standard Specification ASTM B 708 -05 for Tantalum Ribbon, Tantalum Alloy Ribbon, Tantalum Strip, Tantalum Alloy Strip, Tantalum Foil, Tantalum Alloy Foil, Tantalum Sheet, Tantalum Alloy Sheet, Tantalum Plate, Tantalum Alloy Plate.
This specification covers unalloyed and alloyed Tantalum Ribbon, Tantalum Alloy Ribbon, Tantalum Strip, Tantalum Alloy Strip, Tantalum Foil, Tantalum Alloy Foil, Tantalum Sheet, Tantalum Alloy Sheet, Tantalum Plate, Tantalum Alloy Plate as follows:
1. ASTM B 708 -05 UNS R05200, unalloyed tantalum, electron-beam furnace or vacuum-arc melt, or both.
2. ASTM B 708 -05 UNS R05400, unalloyed tantalum, powder-metallurgy consolidation.
3. ASTM B 708 -05 UNS R05255, tantalum alloy, 90% tantalum 10% tungsten, electron-beam furnace or vacuum-arc melt, or both.
4. ASTM B 708 -05 UNS R05252, tantalum alloy, 97.5% tantalum 2.5% tungsten, electron-beam furnace or vacuum-arc melt, or both.
5. ASTM B 708 -05 UNS R05240, tantalum alloy, 60% tantalum 40% columbium, electron-beam furnace or vacuum-arc melt.