For Parkside Cordless Grass Trimmer(4pcs, Black) The winding direction of the thread bobbin is indicated in the bobbin case of the thread bobbin - the arrows on the cover of the bobbin case indicate the direction of rotation of the motorInstallation StepsRemove the battery from the deviceOpen the bobbin case by pressing the two release buttons on the bobbin case at the same timeTake off the cover of the bobbin case and take out the bobbinPush the thread ends of the new thread spool out of the slots in the trimmer spoolInsert the new bobbin into the bobbin case so that the arrows indicating the direction of travel are visible on the bobbin after it has been insertedThen put the two thread ends through the opposite eyeletsPut the cover back on the bobbin casePull on the ends of the thread and repeatedly press the locking button until the two ends protrude. Colour: Black Size: Diameter 1.6mm Package Contents: 4pcs Compatible Parkside PRT 550 A1 Spool Warm prompt: 1.As different measuring methods,it will occur 1-3 cm deviation about the items,please ensure that it is okay for you before ordering. 2. Because of different monitors and lamplight, the picture may not reflect the actual color of the item, really thank you for your kind understanding 3. Only the above package contents, excluding other products. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.