The ornamental design for a grab handle for roundtube, as shown and described.
FIG. 1 is a perspective view of a grab handle for round tube showing my new design;
FIG. 2 is perspective view of the grab handle for round tube shown in an alternate configuration without environmental structure;
FIG. 3 is third perspective view thereof;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a rear elevational view thereof;
FIG. 6 is a left side elevational view thereof;
FIG. 7 is a right side elevational view thereof;
FIG. 8 is a top plan view thereof;
FIG. 9 is a bottom plan view thereof;
FIG. 10 is a perspective view of the grab handle for round shown in an alterante configuration in an extended position; and,
FIG. 11 is another perspective view thereof.
The broken line strap attachment in FIG. 1 illustrates environment and forms no part of the claimed design. All other broken lines in the figures are for the purposes of illustrating portions of the grab handle for round tube that form no part of the claimed design.