The 5.5s are Leatt's more protective line of chest protectors. The Chest Protector 5.5 Pro HD is the Top Of The Line version of the 5.5 chest protector line. Specifically designed to meet the highest safety approvals for front back and shoulder impact protection. The Pro HD has added Hardshell flank protection lined with 3DF foam. This flank protection overlaps with the front and back plates creating an integrating multilayer protection area over some of your most vulnerable parts. Three dimensional design with eight multi layer articulating plates for a great fit. It has also been designed to integrate perfectly with all Leatt neck braces although it works equally well without a neck brace. Exclusive FlipFit front and rear movable plates allow your neck brace to fit under the protector for outside the jersey use or wear the protector under your jersey and your brace can still fit over the top. BraceOnTM strap system attaches the protector to the neck brace yet provides independent movement of body brace and chest protector. The 5.5 line of protectors are the best fitting most protective line of hard shell protectors available today.