This is the Trident Medium Size Slate 4x6 with Plastic Clip Features: White waterproof slate in a medium size Hook-on clip for easy attachment to belt or BC Use for underwater communication or poolside notes Dimensions: 4 x 6 (10.16 x 15.24cm) The Trident Underwater Writing Slate with Clip 4 x 6" (10.16 x 15.24cm) provides a simple but useful diving and pool accessory to keep on hand."