Secure hold for hoses and tubes in the aquarium:
The filter tubes of external filters need to be securely fixed to the aquarium glass panes so that they cannot accidentally slip out, yet glass bars on the upper aquarium rim can make this more difficult. The JBL FixSet includes 2 spacers of different lengths which will fix the tubes/hoses correctly, even where glass bars pose a potential hinderance to attachment.
Rubber suction cups age over time. The harder the water (a lot of magnesium and calcium) the faster the rubber hoses and suction cups age. If the suction power decreases or is no longer guaranteed, they definitely need to be replaced.