Chikwama chamkati cha membrane, chomwe chimadziwikanso kuti chikwama cha nsalu cholumikizira kawiri, ndi thumba la thumba lomwe limakhala ndi matumba a HDPE kapena LLPE mkati mwa chikwama chokhazikika.
Matumba amkati a membrane ali ndi mphamvu yayikulu, chinyezi chonyowa, chinyezi, komanso katundu wothira madzi, amagwiritsidwa ntchito feteleza wopangira, malo opangira mitengo, etc.