The Hollis Signal Marker Buoy (SMB) is a great safety device that all serious divers carry on every dive. The SMB is the smart-way for a diver to mark their location when making safety stops, completing mandatory decompression-stops and signaling the boat if they surface a distance away from the boat. Buoy is a Closed Cell Design made from Durable 300-D Polyester material with Radio Frequency (RF) Welded Seams. The Hollis SMB also has a Sturdy Nylon Webbing Strap Loop with a Stainless Steel D-Ring for attachment to a Reel or Anchor Line along with a Wrist Lanyard for Hand-Held Use.