I think Nuts is technically right, but most people drop the "Infiniti" when referring to the os-zip, though I acknowledge there's also a lower-end version (Xflex). At least Dogfunk corrected the name and the description. Also, the (Infiniti) os-zip differs from the Infiniti x-zip in at least one way besides the entry style. The latter is 100% ultra stretch, whereas the os-zip has less stretch in the core, hips, and upper legs. Arguably there's no need for extra stretch there, but one effect is that the x-zip in a given size can generally accommodate more sizes of human. The exception is people whose necks are too small for the the unadjustable neck of the x-zip. It should border on uncomfortably snug when you first try it on out of the water.