Enamel keychains are pretty common, but these have an unusual twist: Two kinds of enamel (thick clear, and red) over a silghtly 3D design. Finger waving Sonic, Standing tails and the same leaping Eggman are on each of the 3 chains. The thick clear enamel covers the 3D-ness of the design, keeping it (and the red shiny enamel) safe from wear among keys. 

There's also a blue set which is identical, except for the fact that here, the enamel is a dark, navy blue instead of red.