Before buying, make sure you choose the right size!
1. When buying collars, measure the dog's neck and choose the appropriate collar size. Remember that the circuit of the dog's neck should be at ease in the given size - this will avoid too tight or too loose collar.
2. Harness - measure the dog as in the picture below - neck, chest, back and sternum length. Here, too, choose the size of the harness so that the dog's dimensions are more or less in the middle of the dimensions of the harness - so you can easily adapt them to the dog and they will fit perfectly.
3. Bed - there is no rule - some dogs and cats like tight lairs, where they roll into a ball and feel bad on large surfaces - the other way round - the best would take your whole bed :). So it will be useful here not so much measurement as knowing your pet's preferences.