The Letus35 SONYEX1 is an optimization kit designed specifically for the Sony PMW-EX1. The kit comes equipped with a achromatic lens using a 77mm thread ring. The lens acts as a replacement for the stock achromat. The result is higher edge-to-edge detail and in better overall image quality.
Note: You must have the Letus Extreme with a removable rear achromat for this kit to function properly.