Our polystyrene line squares are available in white, yellow, orange and glow-in-the-dark and are { 3.5 in | 8.8 cm } long and { 2 in | 5.1 cm } wide.

Line Squares (also called REM - Referencing Exit Marker) are preferred over line arrows for setting up traverses or circuits because a directional marker on the line could be misinterpreted as pointing away from the closest exit - disastrous in an emergency. Line squares can serve many non-directional purposes underwater from marking a distance during survey to marking an archaeological or geological feature underwater. The large writing area also makes them perfect for penetration markers on the main line or a side passage.

The rem - referencing exit marker - a so-called hybrid marker was introduced by Bill Philips, a cave diving trainer and explorer from Mexico.