The Bottom Line TBL 100 Series Computer Sonar is a vintage fishfinder designed for outdoor fishing activities. With a 4-inch display size and a resolution of 160 x 160, it provides clear depth readings. This electric-corded sonar features a depth indicator, depth alarm, and sonar sensors for accurate readings. Made of plastic and metal, this black computer sonar by Bottom Line is a reliable tool for anglers looking to enhance their fishing experience.