Jennifer Aniston is "overwhelmed" by her eight carat diamond engagement ring.

The 43-year-old actress was thrilled when boyfriend Justin Theroux proposed to her on Friday and she couldn't be happier with the actor-and-screenwriter's choice of jewelry for her. "It's a huge emerald-cut diamond. It's a rectangle with tapered diamond baguettes on the sides. It's beautiful. Just after Jen got engaged, she called all her friends and told them about it. She was so happy and said she loves the ring. I think she was overwhelmed and overjoyed by the size and beauty of it!" a source said.