Looking for an alternative to traditional knob & post-attachment arms? The J.L. Childress Crib Mobile Clamp safely and securely attaches mobile to your baby’s crib railing with a padded clamp. Large rubber pads help protect your crib railing from scratches and damage. The clamp easily opens 2” wide and features a safety button that locks it into position. Recommended use from birth to 5 months. The clamp is naturally portable, making it perfect for all on-the-go adventures. Assembled height is 18”.