Sonar skins are a CS:GO skin family that currently features only one member, it being MAG-7 | Sonar. The skin itself was lightly stenciled in turquoise and can be obtained by opening the Glove Case. The skin is also a part of the Glove Collection and is available in four different exteriors, excluding the Battle-Scarred version, however, all other exteriors can have the StatTrak technology attached to it.
In terms of value, Sonar skins are considered to be cheap, ranging in price from a couple of cents to a couple of dollars.
Check out other CS:GO skins families: