V4 AutoTrickler kit comes with everything below. You should not need to replace these parts through regular use (i.e. they will not wear out). Some people like to get a second cup and some people have cracked their windows by dropping them. We've bundled these parts for convenience, but do not feel like this is a necessary purchase.
 
Glass Cup
V4 Centering Tray
V4 Funnel
2x V4 Windows
V4 Timing Belt (small tube)
V4 Timing Belt (large tube)