The Rogue RDA is a great top air hole RDA, but it has a small drawback: the top cap is very loose, due to the ridiculously undersized O-rings on the base. It's the two O-rings visible in the photo below:
For a perfect fit, simply replace them with 19x17x1 O-rings (i.e. 19 mm outer diameter, 17 mm inner diameter, 1 mm section). I got mine from Co-Joint in Belgium (article no 1103539, "O-ring Ø17x1 NBR-70° Sh.") but they're probably available from any well-stocked O-ring distributor.
For a perfect fit, simply replace them with 19x17x1 O-rings (i.e. 19 mm outer diameter, 17 mm inner diameter, 1 mm section). I got mine from Co-Joint in Belgium (article no 1103539, "O-ring Ø17x1 NBR-70° Sh.") but they're probably available from any well-stocked O-ring distributor.