These are great for smaller plants/pots that are not tall enough for the full size terracotta spikes, and the adjustable water bottle adapter firmly holds the plastic water bottles in place. They are rather pricey, however, especially when compared to many of the standard 8" long spikes (these are 5"). So, I tried a couple of lower cost alternative options that have water bottle adapters, which still cost a lot more than the stand-alone 8" spikes: one came with adapters that hold well but with 8" spikes, and another came with 5" spikes but the adapters do not hold well at all (I ended up taking out the adapters and using a larger 1 liter water bottle inserted directly into the spike and this seems to be working). So, going forward, if I buy more for smaller/shorter pots, I'll probably buy the lower cost 5" spikes with lousy adapters that I'll just toss.