[Persuasion] You roll an 11 (required 9). Success!

You volunteer to wear the ring, and mention that you were just wearing it earlier.

Moondancer: "Fine by me."

The ring floats to the base of your tail, and clasps around it.

You equip Ring of Alter Sex. You are now a stallion.

Moondancer: "Interesting, but it could all just be a common Disguise spell. Now, hold still. This might feel a little weird..."

Moondancer's horn lights up as she begins to cast a spell on you. A tingling sensation flows through your entire body, and lasts for a few seconds.

Moondancer: "Wow... there's no mistake, this ring really has been bound with a powerful transmutation spell."

Sweet Biscuit: "What's the difference?"

Moondancer: "Common spells like Disguise are illusion spells. They alter our senses, and make us believe that something's changed when it truly hasn't. However, putting on this ring physically transformed our friend here into an actual stallion.

I assume taking off the ring triggers the spell again, and turns the wearer back to normal. This means that if the ring broke while he was wearing it, he'd probably be stuck like this until he found somepony able to either fix the ring, or cast the spell to change him back."

Moonflower: "Oooh..."