Just got a sample today from e-clam it says it is a 1524, they actually sent 2 of the same ones: they do NOT have the circle indent in each cube, feels thicker than the circle indent ones..but they were hard to separate and hard to close. I'm thinking they are a step above the impacts 1524C but still not as good as impacts regular 1524. I THINK the circle indent ones are probly the 1524C. Haven't poured in em yet so don't know about the plastic smell. HTH