Vivobarefoot Primus 3.5 Womens size 38 eu 8US Worn once to try on The Primus Lite 3.5 is our original training all-rounder, reimagined with a new upper to get us closer to circularity. Made for moving naturally and building natural strength during runs and wide-ranging training disciplines, it’s perfect for experienced barefoot cross-trainers and those new to barefoot performance.