Silica Sound glass guitar slides are handmade with a thickened end to  promote a unique grip on the tip of your finger, as well as added mass for better sustain. They are unlike any other glass guitar slide in the way they feel, sound and look.

Silica Sound brand guitar slides are the original hand-blown glass guitar slide made with a tapered fit.

sil·i·ca  /ˈsɪlɪkə/ Pronunciation Key - Show Spelled Pronunciation[sil-i-kuh]  –noun
the dioxide form of silicon, SiO₂, occurring esp. as quartz sand, flint, and agate: used usually in the form of its prepared white powder chiefly in the manufacture of glass, water glass, ceramics, and abrasives.

sound  |sound|  -noun
vibrations that travel through the air or another medium and can be heard when they reach a person's or animal's ear.