ZipSider Style TPU/PU Toughsider sole OrthoTec PU innersole Fully lined Original SP comfort & safety The 961020 'Black ZipSider Boot’ from Mongrel is from the SP Non Safety Series. Not everyone requires a steel toe-cap. So Mongrel has provided a number of styles featuring all the best of SP design and comfort without the metal cap. The range includes everything from riding boots to classic elastic sided designs. Including the OrthoTec Air innersole and with sole constructions and materials to match the design - they're suitable for executives to landowners and a whole range of workers in between.