A class 4 microprobe was a specific type of microprobe that was used by Starfleet during the late 24th century. The USS Voyager carried these microprobes. While inside a nucleogenic cloud being in 2371, USS Voyager used a class-4 microprobe as a diversion to draw the multi-polar charges from the creature while it "sutured" the wound with nucleonic beams. The diversion was ultimately successful, as were the repairs to the creature. (VOY: "The Cloud")