These Dimmable plastic ST64 bulbs have a standard E26/E27 base so they will fit into any existing string lights with a E26 Medium base.

Product Specifications:
Bulb Type: LED Filament Light Bulb
Bulb Shape: ST64 Plastic "Signage"
Wattage: 1.6-watt (Energy Saving)
Brightness: 121 Lumens
Voltage: 120V
Dimmable?: Yes, Dimmable.
Light Color: Warm White 2700K
Material: Polycarbonate
Base: Standard E26 Medium Base

LED Filament 2-Watt LED ST64 Sign Shatterproof Light Bulb, E26 Medium Base Video