Spreadshirt Golden Ratio Fibonacci Spiral Men's Premium T-Shirt Designed and printed in the USA. In geometry, a golden spiral is a logarithmic spiral whose growth factor is . The golden spiral can be found in the tiniest sub-atomic particles of the microcosm to spiral galaxies of the macrocosm. If you love the science of aesthetics, then this This premium t-shirt is as close to perfect as can be. It's optimized for all types of print and will quickly become your favorite t-shirt. Soft, comfortable and durable, this is a definite must-own and a Spreadshirt recommended product. 100% cotton (except for heathered colors); Fabric weight: 5.29 oz (heavyweight). For best results and to maximize durability machine wash cold, inside out and tumble dry on low heat. Official sizing (width x length measured in inches): S (18" x 28") | M (20" x 29") | L (22" x 30") | XL (24" x 31") | XXL (26" x 31.5") | 3XL (28" x 32") | 4XL (30" x 34") | 5XL (32" x 35").