AP Valves SMB closed - This is the closed version of AP Valves SMB - developed exclusively by the A.P.Valves' design team - it has what appears to be an open ended base but as soon as you fill the SMB the internal baffle is forced shut preventing the SMB from accidentally deflating on the surface.
The AP Valves SMB also features a stream-lining flap which closes over the mouth when used in a current to prevent any sea-anchor effect.
The AP5 over-pressure / dump valve on the SMB prevents the buoy from bursting and allows deflation after use. Simply attach a line or reel to the SMB and you have a superb decompression marker buoy and also a buoy that can be used as a standard SMB.