Designed for small seed like radish, the M-12 seed roller has 12 round holes, 13/64" (5mm) in diameter. Spacing is adjustable from 1-5” apart depending on seeder sprocket combination. Seeder rollers have slots/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.