Ultimate stretch without compromising warmth for anyone who loves the feeling of unparalled mobility. The Seek Amp 4/3 Back Zip features our new Max_Flex outside lining in the entire shoulder area & arms. Freedom of movement is key in this crucial area, no matter if you paddle for waves or hold on to your kite or sail. The secret for optimal heat retention lies in ION's super flexible Hot_Stuff 2.0 thermo lining combined with toasty warm Plasma_Plush 2.0 on the back against wind chill. On top, light & stretchy limestone neoprene insulates and adds up to flexibility thanks to its super foamy structure. Seek Amp Backzip models feature additional protection pads at the shins.