★There's no low profile bracket since the combined height of the adaptor card and OCP card would be more than 8cm. Adaptor Cards RGB/ARGB. Unit content: one adaptor, a high profile bracket and screws.
I bought two of these cards to test and they are pretty awesome. The ones I bought are referenced as 'OCP adaptor for all'. I was able to grab two ConnectX4 MCX4411A-ACAN off another seller on eBay for $25 each to test and they work as expected.
I think $18 is a pretty good price to be able to reuse decommissioned OCP cards that usually go for pretty cheap compared to their PCIe variants. I don't know if OCP type 2 will work with this adapter as the seller mentioned that they do not have access to type 2 cards to test.
Here are some iperf3 tests I ran from my computer to my NAS over the two ConnectX4 cards: