Lightpipes are usually constructed from optical grade materials such as polycarbonate and/or acrylic.  These materials excel at transmitting visible light from the pcb to the front board when used in combination with a lightsource, usually from an LED.  Lightpipe shapes are usually classified into two distinct categories: rigid lightpipes and flexible lightpipes.  Rigid Vertical lightpipes carry light in a straight line, while rigid right angle lightpipes redirect light across their body out to the focal exit.  In contrast, flexible lightpipes bend light thanks to their predetermined bend radius.  Flexible lightpipes have the ability to better accommodate for offsets in lightpipe and lightsource positioning, thus providing additional design flexibility.  Due to their flexible body nature flexible lightpipes are usually only offered in very small diameters, (1mm or less), thus limiting their efficacy to specialized and small applications.