Wheels Manufacturing Wheels Manufacturing Standard Thru Axle Cap Set – Purple. Personalize and protect your bike with Thru-Axle Caps! Designed to look great and protect your bikes thru-axles from bumps and scrapes machined from 6061 series aluminum for durability. Sold in sets of 2 and press directly into both ends of Wheels Mfg thru-axles adding just the right amount of bling on both sides of your bike.