This is a small replacement core for Susty. (2 replacement cores per pack) Remove the top cap and remove the core inside, then insert the new core. When replacing, please check whether the old core material is left inside the main unit, and use a new core. Model Number: C-0014; Operating Temperature Range: 12°F - 104°F (5°C - 40°C); Humidity Range: 20% - 80%; Refill Size: W0.16 x D0.2 x H4.3 inches (W4 x D4 x H110 mm); Weight: Approx. 0.05 oz (1.5 g); Estimated replacement: Approx. 6 to 9 months.