XCEL Kids XCelerator Shortsleeve Neoprene Shirt with Quarter Zip Neck Swim Surf The Xcelerator is a lightweight top with 1mm body, UltraStretch 1mm top sleeve, and UltraStretch 0.5mm under sleeve. Front quarter-zip makes it easy to put on and take off. Flatlock seams for comfort, super light Nylon 2 front to prevent over-stretching and filling up with water. Ultrastretch sleeves and back make for great performance and easy on and off. Elastic cord side cinch and front loop to tie to boardshorts to secure top from riding up. Contoured sleeve design for maximum performance and comfort. 0.5mm soft Titanium lined collar.