Micro loops are a type of hair extension technique that uses virgin human hair and does not require any heat or glue for installation. The extensions blend well with natural hair and can be easily maintained without any residue or adhesive. They come in bundle sizes of 100 strands and are reusable for up to a year. The number of bundles required for adding length and volume depends on the natural hair thickness. For fine hair, one bundle is sufficient, while for medium to thick hair, two bundles are recommended. For a full and voluminous look, three bundles are required. The cost of micro loop hair extensions can vary depending on factors like the length and density desired, the quality of the bundles, the location, and the work required to achieve the desired result.