Instrumentation grade stainless steel tubing is different than stainless pipe as it is defined by the outer diameter rather than the inner diameter such as is the case with stainless pipe. 1" stainless tubing has a 1" outer diameter and varying thickness of its wall. Therefore stainless tubing serves as structural. 1" stainless pipe (seamless and welded) has a 1" inner diameter and different schedules of thickness. As tubing is used for structure, pipe is used to conduct material (solid, liquid, gas) flow. Instrumentation grade stainless tubing has a fine finish in both the inner as well as the outer diameter. Stainless tubing comes in both 304/304L as well as 316/316L stainless grades.