The Full Cover blocks are complete graphics cards liquid cooling blocks, designed for the die-hard enthusiasts who seek the optimal cooling solution for their graphics card. A Full Cover water block's main advantage is that it cools all heat generating components - GPU, RAM IC and VRM (see Glossary) by a single cooling unit and in a single coolant pass.
But Acrylic Full Cover block is shorter than the Acetal one, you may ask.
All Full Cover water blocks from the same product family have the same copper base thus they cool the same components – GPU, VRM and RAM IC. By definition a Full Cover is a water block that cools these exact components and has no relation to the size of the cooler.
The different length of cover is just for aesthetics purposes. Long top or short top – the performance is the same.