Evans improved EC2 drumheads contain Evans' exclusive and patented Sound Shaping Technology (SST). Sound Shaping Technology allows the drumheads to be fully optimized for each individual size by varying the thickness and density of the damping material, ensuring greatly improved performance and tone across the entire kit. Unlike other heads that lack SST, Evans EC2s contain the ability to balance attack and tone for each size. The result is a drumhead series fine-tuned for attack, tone, length of sustain, and ease of tuning. Packed with a more balanced and pre-EQ'd sound across the full kit, the Evans EC2 with SST will make your toms sound better than you ever thought possible. From the Manufacturer Evans 18" clear EC2 two-ply drum head with Edge Control technology provides a pre-EQ'd sound and a variable damping technique that insures optimized performance for each individually sized drum head.Evans EC2 series features two plies of 7mil film with optimized attack, tone, length of sustain and ease of tuning for each size head. The Sound Shaping Technology (SST) Edge Control ring mounted on the underside delivers an extremely well balanced and pre-EQ'd sound across the full kit by varying the size of the ring for each different head size.For over 40 years, Evans has been a pioneer of drum head manufacturing and design. Known for innovative designs such as EMAD, EC2S, and the Hydraulic series, Evans drum heads are made in the USA in a state of the art manufacturing facility. Acquired in 1996 by D’Addario and Company, the global leader in musical instrument accessories, the Evans brand is synonymous with quality and consistency.