These pens use special ink and a pressurized ink cartridge.  They are purpose designed for use with the Rite in the Rain papers but they also work fine with regular papers. 

Tactical Clicker:  Flat black metal barrel, black ink.  This is not a fighting pen as the 'tactical' implies but just a matte finished cool looking pen that will look right at home tucked into a loop on your web gear.  Think office pen in battle dress.  Internals are plastic.

Trekker:  flat black metal barrel with rubberized grip and a key ring, black ink.  The ring can be used to secure the cap to a bag or harness allowing the short pen body to be pulled away as needed.  Nice firm snap action of the pen to the cap.  A bit small for those larger hands but we like this pen!  It is compact, rugged, and has that quality feel.  This is a field pen, not an office pen.