This beam type coupling can be used to connect two 8mm shafts together. Each shaft is held in place by two set screws, allowing for easy installation. The spiral cut design allows for up to 2° of bending from angular misalignment and up to 0.12mm eccentric misalignment.
If you're having trouble with slipping, you can file a groove into the shaft where the set screws hold it in place. You can also use a Loctite adhesive on the set screws to ensure that they remain in place.