Her sister and the golden ring

Kate remembered the golden ring. She put the silver one in her pocket and placed the golden one where the silver one was. She moved over to her sister's bedroom's door.

"May I come in?".

"Sure. You feeling better?" - Asks Anna.

So she was answered with a yes, which means the effect is different. Perhaps even opposite...

"Yeah. Were you looking for the package with 'Rainbow Tampons' written on it?" - She knew her sister's tampons were normal white ones, from having seen her lose them before.

"Yes, that's the one! Did you find it?"

"Sorry, no, just making sure."

So, the opposite effect with the golden ring, this would be interesting. She was still horny from before though.

"Ehrm, Anna.. your boobs are G cups, right?"

Suddenly, Anna's boobs getting A LOT bigger.

"Yeah, of course, why?"

"Oh, nothing. Just wondering about something... Your boyfriend's 8 inch right?" - Kate asked, knowing he was bigger because she'd heard her sister shout from her bedroom when their parents weren't home, when Anna was having sex, specifically "YES, GIVE ME THOSE 10 INCHES!".

"I don't know how you know, but yeah he is."

"Well, just think it's funny that I'm a chick and I've got him beat on dick size!"

"Wha- What? You're bigger than 8?"

"Well, yeah!" - She swaps her rings behind her back, getting the silver on - "You ever seen a bigger one?"

"No..."

"Would you think less of me if I showed you mine right now?"

"No, sis..."

Kate can see that Anna's starting to get wet down there.

Kate undoes her pants and says "Is that any smaller than you'd like?", as her dick starts to get hard. Anna was sort of a size queen, and she always wanted it bigger in a man. Her perfect size would be about 12, which was what Kate's dick turned into, a 12 inch stick.

"Woow... It's just so big.. and so perfect.."