The 15 pound check valves, part number 150123 have been coming without the direction arrow stick-on label on them. If you hold the cv with the Fresenius part number label towards the left, and look closely at the right half of the body you will see two small arrows cast into the body that are pointing to the left. There is also some lettering cast into that half that says "Smart Products". Those arrows are small and difficult to see, but they are there.

Nice tip! I probably would have been cussing, missing the small detail had I not known about it. Thanks!

Maybe they've updated the housings so they will last from annual to annual again. I've had a several that are failing after only 3 to 6 months of service lately. I guess the did something to cut cost at smart products.....