The following applies as far as the size of the cupping instruments is concerned: The more the skin surface is curved (e.g. neck), the smaller the diameter (2 to 3 cm), the shallower the region (e.g. back), the larger the diameter ( 5 to 6 cm) of the cupping.
Acrylic cuppings (except those which can be sterilized up to 170 °) should not be used for "bloody cupping".
Traditional Chinese Cupping with Ron Farkas LMT for athletic injuries or accidents. (shared youtube video)
Traditional Chinese fire cupping therapy. The treatment is not very painful. The bruises will last for 1-2 weeks. As you can see the cupping is not very difficult and can be easyly done. (shared youtube video)