4 Carat Round Diamond Engagement Ring. A classic, this brilliant center diamond has a cool white color and great clarity. Set in a platinum in a diamond eternity band with over 2.5 carats of matching white round brilliant diamonds. The combined carat weight of this ring is over 6 carats. Rings like this and many like it can be found at our Newport Beach showroom located on PCH, north of Laguna Beach, Corona Del Mar and west of Costa Mesa.