Hello John,
What's the model of your pump?
Sorry that the size of BP-WTP-OD5-BK is not shown on the website.
But it is for the D5 pump. If your pump is D5, it is compatible.
Yes, BP-WTP-O50-BK and BP-WTP-O10-BK are the same type of o-rings that would fit g1/4 male threads.