BCY Power Grip Serving Black .018 100 yds. 65808. Tough and durable material with a resin coating. Can be used for end servings (.018) center servings (.021/.025) or crossbow center servings (.032). Package Contents: BCY Power Grip Serving A blend of tightly braided spectra and nylon yarn. Tough and durable material with a resin coating. Can be used for end servings (.018) center servings (.021/.025) or crossbow center servings (.032).