Is this good for diabetic cats?

Yes.  Low glycemic ingredients may reduce or eliminate the need for insulin in diabetic cats. Diabetic cats with the highest remission rates (greater than 80%) have been reported to have feeding diets with approximately 6% of energy from carbohydrates. Dr. Elsey’s cleanprotein™ delivers only 5% energy from carbohydrates as compared to leading Dietetic Management foods with levels as high as 13%.

An informative study: