The Engagement finger ring is presented by Evolved (manufacturer) and EdenFantasys.

This excellent addition to any bullet lover's collection is designed for pinpoint stimulation. The ring stays in place on your finger. The wire's long enough to move around, but stays out of the way. It's light and compact making it excellent for travel. Its vibration strengths and pulsation variables are perfect for beginners and experienced users alike. And it comes with two sets of three watch-style batteries.

Just don't offer it to your lady instead of a diamond. She won't be amused.