The X-12 seed roller has twelve round holes, 5/32" (4mm) in diameter. Spacing is adjustable from 2-5” apart depending on seeder sprocket combination. Seeder rollers have cups/holes to cup the seeds to allow for singulation. Made from anti-abrasion plastic to prevent build-up of static electricity that causes seeds to stick together. Great for Onion, Radish, Kale.