Review on Lasenersm 4-Pack 2.53oz /75ml Refillable Roll-On Bottles - Plastic Rollerball Containers for Essential Oils, Perfumes, Balms - Leak-Proof, Reusable, DIY Thin-Waist Style by Christine Bergseth

I use these reusable roller bottles to store and apply the DMSO-based transdermal NSAID solution I make. They hold quite a bit of liquid and the large tolerance around the nylon reel allows liquid to flow out and roll very easily. My only concern is the occasional accidental leak at the junction of the main reservoir and rollerball assembly. There are just a few thin plastic threads holding these two pieces together and this connection is independent of the cap/cap threads. I've noticed leaks on two occasions: (1) when I shook the liquid even slightly (with or without the main cap on) and (2) when I unscrewed the main cap and inverted the roller unit, a few drops often spilled onto the floor, countertop or something unintentional on my skin. The way I combated this tendency to leak was to always tighten the roller and ball assembly on the bottle separately, both when removing and removing the main cap. I'm also becoming less careful with over-tightened connections. Despite the fact that the #2 bottle's plastic walls appear to be quite flimsy and the small number of threads attaching the reel assembly to the main pod, I haven't noticed any breakage or crossover of the components. I have also NOT put these containers through the ultimate travel test and don't think I ever will, throwing them in my suitcase without first zipping them or some other more airtight container.