Alpinestars Bionic Air Back Protector Insert Features The Bionic Air Back Protector insert is CE certified to the latest back protector standard and offers the street rider superior levels of comfort and performance in an ergonomic design. CE Certified Level 1 to the LATEST back protector standard (prEN1621-22010) allowing a slimmer, more ergonomic design. Slips in to your jackets back protector pocket to give you high levels of protection on the street without hindering riding comfort. Innovative Dual Density Honeycomb Technology (DDH) combines two different honeycomb structures to offer lightweight impact protection with exceptional breathability and comfort Outer Honeycomb plate - Made of Polypropylene provides an outer structure to protect the back from penetrating injuries, as well as dissipating impact force over a wider area Inner Honeycomb foam - Made from a special elastomeric compound, this light and flexible impact foam absorbs transferred energy Please see below chart for protector measurements Size Measurements Medium 16.5 Height 10 Widest Point 9 Narrowest Point Large 19 Height 10 Widest Point 9 Narrowest Point (function() var cycle true ('table.sizechart tbody tr').each(function(row) classname (cycle !cycle) 'light' 'dark' row.addClassName(classname) ) )()