US D618086 S1
The ornamental design for a filament spool, as shown and described.
FIG. 1 is a top front perspective view of a portion of a filament spool;
FIG. 2 is a bottom front perspective view thereof;
FIG. 3 is a top view thereof, the bottom of the filament spool being flat and unornamented;
FIG. 4 is a front view thereof;
FIG. 5 is a rear view thereof;
FIG. 6 is a left side view thereof; and,
FIG. 7 is a right side view thereof.
Features illustrated with dashed lines are not considered features of the invention being claimed, but rather illustrate an exemplary environment for the claimed features illustrated with solid lines.