I have tried them and do not like them ... difficult to get the pens in and out. . If you make a slip and the pen contacts the zipper you will get scratches on the pens. . Also, some of the spaces are too close to the edges or zipper and cannot be accessed .
I prefer the "suitcase" shaped, hinged lid type cases. . They hold 24, 32, or 48 pens. . The 48 pen one holds only slimlines, so I would not buy. . I prefer the 32.
One problem with these is that the top and bottom lining, into which the elastic pen loops are threaded, are only lightly glued to the external top/bottom pieces of the suitcase. . It does not take long before the glue gives way and the linings fall toward each other. . My only solution to that is to store these cases with the weight resting on the hinged edge, that is with the closure clips facing up. . In this way, the weight of the pens does not pull the linings away for quite a bit longer.
Another thing ... if you insert 32 pens in the 32-pen case, it does look too crowded.
So, I only use every other space with the resulting storage/display of only 16 pens.
My final word is that pens larger than the Jr. Gent size are too big for these cases, and also too big for the zippered cases.
Hope this is useful information for you. . For non-display usage, you can fill all spaces with pens, but I prefer open top trays.