Looking to create an artificial ice core using a 4" PVC pipe as a mold? (Or a giant cylinder of jello? Or just to hold similarly-sized objects in a short length of pipe? Or...) This little hurricane symbol tension-holds itself in a 4" pipe and features several clips for 4 mm capsules, such as these encased resistive temperature detectors (RTDs): https://www.adafruit.com/product/3984 The central hole slides around 1/2" nominal copper pipe, helping to center both the clip and the pipe. Designed as part of research sponsored by the National Science Foundation.