These bamboo embroidery hoops are suitable for working all kinds of crafts from needle arts to fabric painting,keep fabric taut while working embroidery or other forms of needlecraft. How to use and adjust the tension ? 1.Frist of all,unscrew to release the inner hoop, place your chosen fabric over the inner hoop. 2.Then lock into place with the top hoop and screw in to tighten. 3.These embroidery hoops have a brass adjustment screw that you can tighten when necessary to keep the fabric,the fabric can be stretched drum taut and stays that way during the process. 4.Final,inspect the hoop whether it is tight enough,and you can start your work. Specification: Material: natural bamboo Approximate circle size: 17 cm, 20 cm, 23 cm, 26 cm Color: Wood color Weight:7g(17cm),17g(20cm),21g(23cm),38g(26cm) Package included: 1 x 17 cm (6.7 inch) Embroidery Hoops 1 x 20 cm (7.8 inch) Embroidery Hoops 1 x 23 cm (9 inch) Embroidery Hoops 1 x 26 cm (10.2 inch) Embroidery Hoops