the bu-29 is a flexible pvc insulator for bu-27 series clips. 

model #: bu-29-2
category: insulators
weight: 8.8 g
dimensions: 3.5" (l), 0.89" (w), 0.89" (h)

mueller’s bu-29 is used to electrically insulate bu-27 series clips.
• overall length 3.5” (89mm), large id = 0.6” (15mm), wire-end id = 0.22”
(13mm)
• material: insulator flexible pvc
• rating: dielectric strength 5kv at thinnest cross section
temperature -20°f (-30°c) to 160°f (71°c)

bu292