I purchased this and it fits the weed eater attachment STA1500!!!
EGO Power+ ABB1203-1 Commercial Metal Blade Combo Kit for EGO 56-Volt Lithium-ion Cordless Commercial String Trimmer STX3800, black https://a.co/d/i1CtMiI
This is the link to the String Trimmer I put the blades on
EGO Power+ STA1500 15-Inch String Trimmer Attachment for EGO 56-Volt Lithium-ion Multi Head System https://a.co/d/hHdseD8