FIG. 1 is a perspective view of a process tube;
FIG. 2 is a side plan view of the process tube;
FIG. 3 is an end plan view of the process tube;
FIG. 4 is a top plan view of the process tube;
FIG. 5 is a bottom plan view of the process tube; and,
FIG. 6 is a cross-sectional view of the process tube taken along line 6 in FIG. 4.
The broken lines immediately adjacent the shaded areas represent the bounds of the claim, and other broken lines illustrate portions of the process tube that form no part of the claimed design. None of the broken lines form a part of the claimed design.