The LT4 Extender can be used with any LT4 trekking pole to make it taller when used to set up under a taller shelter.  The extender simply fits between the two existing LT parts and the downward force of the shelter tension holds it in place.  The LT4 is still adjustable when using the extender.  The carbon fiber LT4 extender adds about 17 inches to the length of a Lightrek4 for a measly 22 grams (0.80 oz).  This part can NOT be used to lengthen a trekking pole for hiking with, it is ONLY meant for shelter setup.