This configuration is based on the features of the standard "Twister" pen.
The "Double-Exposure" option involves machining two rows of holes in the cap and installing a glowing insert inside to help you locate your pen in the dark.
This has proven to be a popular feature with those who travel, as the pen (or whatever it is attached to) can be located quickly in dimly lit areas or even in total darkness. You have a choice of either a green or blue insert.
A satin finished Twister Pen (as shown) with the "Double-Exposure" option is $800.00, which includes shipping and insurance in the continental US. (Sorry, no foreign orders can be accepted.)