The Q-12 seed roller has twelve round holes, 5/16" (8mm) 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. This item is shipped directly from our supplier, please allow 7-10 business days for delivery.