They are a weak link, but are ok for a few years of use. When you install them, don't put the tee under a side-load or overtighten the clamps. Be nice to your plastic tee, and keep a spare in the truck for a roadside fix.
It is sold to flush the system but can be used to burp a 40 as well. I always found if you parked it on a steep uphill grade and let it idle with the heat running for 10 minutes it burped itself just fine.
What is the purpose of this? For flushing or burping?
They can quickly bleed air at the back of the engine and for that, they are nice, but not critical. Once you flush your cooling system once, if you keep quality coolant in it and change it, you really don't need to flush regularly.