Night vision scope adapters that attach to your scope and add night vision capabilities come in digital IR, thermal, and I2 (intensifier tube) models.
It seems that the I2 and thermal models add a lot of weight and length to your scope setup and the digital models are smaller and more compact.
One thing to consider is that the digital and thermal just use your scope as a magnifier for a mini display on the scope facing part of their device. Put it on a quality scope and you loose all the benefit of the scope’s optics.
Digital Crosshairs 1000 night vision clip-on is different. It mounts to the eyepiece of your scope and uses the scope’s optics fully. The better your scope the better performance to expect. This eyepiece mount is easy to install and remove. It’s compact size only adds about 30 oz to the weight of your gun, including the batteries.
If sit an wait hunting, size and weight can be managed but when you are walk and stalk hunting at night every ounce matters.