The value priced Dive Alert™ Orange SMT is { 5.4 ft | 1.6 m } by { 8 in | 20 cm } and inflated with your second stage regulator. The nylon strap at the top provides an attachment point for a light or slate and two strips of reflective tape across the top significantly increase visibility. Constructed of durable 400 denier polyurethane coated nylon material in high visibility orange on both sides and including two hook and loop straps at the bottom to retain a tidy compact roll for storage.

The semi-closed design is a hybrid of open and closed types that is open at the bottom and incorporates an funnel-shaped (aka 'duck-bill') internal baffle that allows the tube to be inflated as usual with a regulator second stage at depth, but prevents the tube from unintentionally deflating should it fall over while on the surface. The hybrid marking tube includes an over pressure valve (OPV) to allow excess gas to vent during ascent and a pull dump to deflate the bag before boarding the boat or when being rolled up for storage.

NOTE: The hybrid SMT is not fully closed by design and if you inflate it when dry (i.e. at home, to 'test' it), you will discover gas slowly leaks out through the bottom baffle. This does not cause a problem in actual in-water use, where the water will cause the baffle to seal. Although a marking tube should not be used as a lift bag, for emergency purposes a fully inflated tube may be considered to have approximately { 13 lb | 6 kg } of lift when completely submerged.