Iron Heart 21oz “Shinakaya” Indigo Selvedge Denim Shinakaya is a brand new concept from the mind of Haraki-san, a new 21oz Iron Heart indigo selvage denim with a little give. Specifically designed to make the slimmer jeans series more accessible and comfortable by including 2% polyurethane in the weft yarn of the denim weave for added flexibility. At the first glance, it looks and feels like their signature 21oz indigo selvage denim, but the weft on of Shinakaya Selvage denim is a little darker which gives a darker indigo color overall. Wearing it for a while, you can feel the difference as the denim allows more flexibility and mobility in a proper way without diminishing the essence of how the heavyweight denim feels. 21oz Indigo Selvage Denim. Woven with a double twisted weft yarn which includes 2% polyurethane. Button Fly. Sanforized. Made in Japan. Available in their 666 Slim Straight cuts and 777 Slim tapered cuts. Available now in our store.