I use my Time Timer MOD at our school to keep me and my students on time with work/lesson completion, and I have found that this silicone case is a necessary accessory to protect my timer from breakage (as it drastically reduces accidental falls with its friction against surfaces it is placed upon). It fits tightly enough that it stays on, but it is not too tight that it cannot be taken off when needed. Thank you for making a great case to protect my Time Timer MOD!