The ornamental design for a stringtrimmerhead, as shown and described.
FIG. 1 is a front perspective view of the string trimmer head according to the invention.
FIG. 2 is a rear perspective view of the string trimmer head according to the invention.
FIG. 3 is a front view of the string trimmer head according to the invention.
FIG. 4 is a rear view of the string trimmer head according to the invention.
FIG. 5 is a left side view of the string trimmer head according to the invention.
FIG. 6 is a right side view of the string trimmer head according to the invention.
FIG. 7 is a top view of the string trimmer head according to the invention; and,
FIG. 8 is a bottom view of the string trimmer head according to the invention.
The broken line showing of the lower handle illustrates the environment of the claimed design and forms no part thereof. The remaining broken lines in the drawings illustrate portions of the string trimmer head and form no part of the claimed design.