The Boles Float Rite Indicator is constructed of polypropylene yarn with a swivel in the middle. The key to its effectiveness is its flag; when the indicator and nymph are working properly, the flag is straight up and down. If it isn't upright, then you need to adjust your mend or there is some other problem. Because anglers are visually alerted to problems--and can quickly fix them--they spend more time fishing correctly, so their success rate is higher. Dress the indicator thoroughly with floatant.