surfbeach on 4/27/2012
Firstly, I'd like to point out that I've got this on both sides, on a 75 gram (Palio r57) bat, with 1.5mm sponge both sides; total weight is 150 grams. This was just something I tried, as all my bats total weight was about the 175 grams previously. I've been hitting with my 'robot' for a few days now and am sold on the combination. I liken sprungfeder a4 to sriver which I tried in 1.5mm many years ago.
I loop off both sides and find the control is amazing, and I love the 15% reduction in weight great for hand speed. This is probably not your type of rubber if you need a tacky rubber to produce spin. Maybe a thicker sponge would give it more spin but I won't be going over the 1.5mm any more due to the weight increase, so won't be able to tell you.
I didn't rate durability but the time put in thus far, I'd rate it quite alright.