With double-sided zipper (longitudinal and transverse)

I bought a pretty good and cheap foam mattress, which had an extremely smooth and slippery synthetic reference. This respect I wanted to replace. But a new reference coating on a foam core is not so easy. I then bought two mattress covers (BNP and velamen), but only those for the BNP I sided zipper (longitudinal and transverse) get on the mattress. Although he does not quite perfect, but so far I have found nothing better. I pull on the BNP mattress cover even a normal Frottespannbetttuch about and am quite happy with the solution now. The material quality of the BNP mattress cover I feel as well. So at a purchase price of just over 20 a buy rating, because of the two-sided zipper.