They used to be all we used. However they had to find a new supplier for bicarbonate and had to go with Fresenius as that suppler of bicarbonate and they force our unit to carry some of the optiflux filters in order for them to get the bicarbonate.
Never had a problem with them and they worked pretty well from my standpoint. Kt/V's were consistent and seemed to work great IMO.
Here is a link to the Gambro site that will let you select a filter you use and see what the specifications are for the filter and at what it does at what flow speed.
http://www.usa-gambro.com/Pages/InfoPage.aspx?id=12895