HP HSTNN-DB9Z is an internal lithium-polymer replacement battery for compatible HP laptops, including the listed HP Spectre x360 models.
Its four cells provide a rated output voltage of 7.7 V. The stated energy capacity is 66.52 Wh, with a charge capacity of 8640 mAh.
Listed compatible models are HP Spectre x360 14-ef2000, 14-ea0000, 14-ea1000, 14-ef0000, 2-in-1 14-EF1000 and 14-ea2000. Check the laptop model against this list when choosing a replacement.