Originally Posted by hokiefyd

That one has a thin plastic chain guard. You can see the little plastic "protuberances" along the circumference where a small plastic screw inserts from the chainring side, in the 10:30, 4:30, 6:30, and 1:30 positions. That's a plastic guard intended to shield the rider's leg from the chain, or catch the chain if over-shifted off the large ring.