Yes, they are compatible. The HP Photosmart 5520 e-All-in-One printer uses HP 364 ink. HP 364XL ink is for 750 pages, the HP 364 for 300 pages. But it has no influence on the durability.

Quite simply: Yes.

Article 15664282 is compatible with the following devices: - DeskJet 3520 e-All-in-One Series - Photosmart 7510 e-All-in-One Series - Photosmart 7520 e-All-in-One Series - Photosmart B8550 Series - Photosmart C5300 All-in-One Series - Photosmart C6300 All-in-One Series - Photosmart D5400 Series Item 208167 is compatible with the following devices: - HP Photosmart 7520 e-All-in-One Printer (CZ045B)

All compatible devices are listed on the manufacturer's website: https://store.hp.com/SwitzerlandStore/Merch/Product.aspx?id=N9J73AE&opt=&sel=SUP&lang=de-CH&gclid=EAIaIQobChMIhP7CiMeb3AIVr53tCh1VhQ6aEAQYAyABEgJp0fD_BwE&gclsrc=aw.ds&dclid=CJnYx5LHm9wCFZfhGwodEREOJg

Yes, the cartridges are for the HP Photosmart Premium C310a. Correct, the black colour is wider than the colour. https://h22203.www2.hp.com/SureSupply/?searchTerm=HP-Photosmart-Premium-e-All-in-One-Printer---C310a

According to HP's cartridge list, the cartridges with the designation 950 XL must be purchased for the HP Officejet 8600 plus - my ink cartridges have the designation 364XL for the black ink.