Fabric - strong proofed durable polyester, to fit 4 bowls of all sizes.  

Cautionary tale:

So there were these four bowls that went for a night out and during the course of the evening fell in love each with another. The looked into each other's eyes, held out their arms to each other and clasped hands.

"Oh darling" said one to any of the other three (she wasn't too particular, having drunk several shots of Grippo polish with Monkey Grip chasers): "if only we could free ourselves from these canvas restraints we could embrace properly!"

"Steady on Eileen" said the other three all at the same time and in remarkable harmony: "We have a sneaking suspicion we may all be related!"