The Camco 10-Pack Mega Drop-Ins are the all-in-one tank treatment your sensors and tank need to break down waste and tissue. The convenient quick-dissolve formula will stop strong odors for up to 7 days. One drop-in treats up to 40 gallons. Contains no harmful formaldehyde. 10 lemon zest scent drop-ins included. Stop strong odors for up to 7 days No harmful formaldehyde Cleans sensors & tanks | Camco Mega Drop-Ins, 10 pack