Socket weld flange is similar to the slip-on flange in outline, but the bore is counter-bored to accept pipe. Socket welding pipe flanges are typically used on smaller sizes of high pressure pipes. Socket weld flanges are widely used in high pressure systems such as hydraulic equipment and steam lines. Socket weld pipe flanges are attached by inserting the pipe into the socket end and then applying fillet weld around the hub of the flange. This allows for a smooth bore and better flow of the fluid or gas inside of the pipe. An optional internal weld may be applied in high stress applications.