i think im going to buy an alex k showerhead downstem for my gong bong but i have couple questions. sorry if there kinda stupid my downstem i have now is 18/18mm can i buy a 14/18mm since all my other sliders are 14mm and i only have one 18mm slide? also on the site their is two different alex k downstems one is black and one is white is there any difference other than the color label , or are they different showerheads if so which one is better? thanks and sorry if the questions were noobish ive never bought a downstem before Also im going to by a space case because my grinder has aluminum shavings which is dangerous . i think im going to get the 2pc small 25$ and buy a pollen box later. any opinions?