good but hard inflexible plastic-would have suited my purposes better if it were more pliable rubber, it could do some damage if you were using it on a regular basis for "put up-pack-down" gigging because the force necessary to push even small 1/4 " jack audio wires into them, can wear on the cables outer shielding. Not a problem for hardier cable requirements but if using on a Gibraltar rack for example it can mean buying replacement cables sooner than you might expect with the use of Velcro straps-it all depends on your needs and the task at hand, but consider if you would be better with less volume of cabling, to use Velcro strips instead?