Hooks right on most collars up to 1.25” wide and most leashes.   I have actually used on 1.5” also

Rechargeable usb, no replacing batteries, waterproof body, dimming function, durable silicone, lights up to 13 hours on a single charge, the brightest led in its class includes usb charging cable.  Only 17.49 including USA shipping each.

Matrix led rechargeable led pet safety light