Is the nib in a Conid regular demonstrator bulkfiller easily removed from or installed into the plastic nib-feed housing/collar? Or is the nib firmly fixed inside the plastic housing so that the nib can't be removed? What company makes their nib-feed plastic housing/collar for the regular bulkfiller? I know Conid modifies that collar/housing by adding a tube at the rear end. I ask because I'll soon receive a Conid regular demonstrator bulkfiller (flat ends version) minus the nib. I told Conid I'd put in one of my #6 nibs. But after ordering, writing to Conid maybe twice before and after ordering, I then watched the Conid video showing how easy it is to change #6 nibs in the Minimalistica and regular bulkfillers. Having viewed the video, I thought that Conid might have thought from one of my messages to them that I own the same kind of nib-feed housing/collar that screws into one of their fountain pens. You see, in that video the Conid worker simply uses an entirely new plastic nib-feed housing/collar unit instead of pulling out from the plastic nib-feed housing/collar just the nib and pushing into that housing a different nib. Kindly tell me if one of you Conid Minimalistica or regular bulkfiller owners knows about this. Thanks