What is this thing??

I found it in my boyfriends toy drawer with the lube, condoms, handcuffs, blindfold, a remote controlled vibrator, and some complicated strap contraption. Apparently he’s a bit kinky 😍 but I have no idea what this little black rubber thing is?? It feels sticky from silicon lube (not the water based kind). Like he hasn’t cleaned it. Silicon lube doesn’t evaporate like water based lube does, so it may have been there a while 🤢

I’m so curious though??? I’ve seen a lot of weird sex toys but this one is confusing me!