【ABOUT SPARE BLADES】Made of PA6 (Nylon), put the blades in water the night before use them, they will last longer. Good for grasses and thin brush, not for saplings or other hard material.For best use, avoid using this accessory for edging, working alongside brick, chain, or wooden fencing. 【EASY INSTALLATION BLADED TRIMMING SYSTEM】Say goodbye to annoying line trimming system, You do not have to struggle with your trimmer line as it gets stuck.The FourShow unique designed bladed trimmer head is easy to install,Simply push this trimmer head into the stringer socket and it automatically locks in place with assistance from the side push buttons.【PLEASE NOTE WHETHER THE LOCK BUTTON IS THE SAME AS THE ORIGINAL COVER】 【QUICKLOAD BLADES】The FourShow bladed trimmer head , Compatible with Black Decker grass trimmer, Does not require screws or any tools, just load the blade directly, the blade can be replaced in seconds. 【WILDLY COMPATIBLE】The FourShow bladed head compatible with Black Decker:GH400, GH500, GH600, GH610, GH900, GH912, ST6600, ST7000, ST7200, ST7700, ST7701, ST8600, ST9000, CST1000, CST1100, CST1200, CST2000, MTC220, MTE912, NST1018, NST1024, NST1118, NST1810, NST2018, NST2118, LST120, LST136, LST140, LST201, LST220, LST300, LST400, LST420, LST522, LST1018, LSTE523, LSTE525, BESTA510, BESTA512, BESTE620 【PACK OF 20 SPARE BLADES SET】1 Pcs Bladed Trimmer Head + 20 Pcs Quick-load Blades.【For more spare blades,search B09HH5VJDP on Amazon or in our store】 【Upgrade Quickload】 Bladed Trimmer Head,with 20 Pcs Spare Blades,Compatible with Black Decker String Trimmer GH400, GH500, GH600, GH610, GH900, GH912, ST6600, ST7000, ST7200, ST7700, ST7701, ST8600, ST9000, CST1000, CST1100, CST1200, CST2000, MTC220, MTE912, NST1018, NST1024, NST1118, NST1810, NST2018, NST2118, LST120, LST136, LST140, LST201, LST220, LST300, LST400, LST420, LST522, LST1018, LSTE523, LSTE525, BESTA510, BESTA512, BESTE620