Ping Eye 2. The Ping Eye 2 started the revolution in perimeter weighted clubs. The deep cavity allowed weight to be distributed around the outside of the head - resulting in a high moment of inertia (MOI). In simple terms, it meant the clubhead resisted twisting at impact on off-centre hits - so it was - and remains - very forgiving. Ping Eye 2 irons are without doubt the most popular irons in the history of the game. This model underwent dozens of minor revisions through the years, the final changes resulting in the Eye 2+ model, which was introduced in 1990 - but which is so popular it is still available to buy from new Ping today as a special order.