This is an ASA 1.5 inch fixed bored ASA flange with NO O-Ring groove. These flanges are made with weld prep and have tube boring. They are designed to be welded onto tubing. Both sides are smooth with NO O-Ring Groove. They are made of 304 Stainless Steel. 

ASA ANSI flanges come in smooth or grooved flanges, bored or non bored, rotatable or non rotatable, and adapters to other flange types. With tubing sizes ranging from 1 in. to 12 in. diameter and outer diameters from 4.25 in. to 16 in. The Sizes of ASA are from 1 in. to 10 in. The two flanges that will mate can be two alike smooth flange faces or two unlike, one smooth face and one groove face. The flanges are mated together with nuts, bolts and washers. (See graphic below) 

The ASA ANSI flange specification was originally created for use with steam pipes but have now been adapted to vacuum. Diffusion pumps, roots blowers, cryopumps and large rotary piston pumps are some examples of the ASA flange uses. Using O-Rings with Viton, Buna or Silicone they are capable of achieving pressures as low as 1x10-8 Torr. We have a complete line of ASA flanges, adapters, O-rings and bolt kits to fit your most demanding needs.