Many night vision scopes are short and compact and cause position problems for eye relief making you lean forward more than is comfortable or even useable.
The bases here are either for specific night vision sights such as the Arken ones to suit the DNT Zulus.
Or for specific rifle makes where they are extended in length to allow for more flexible sight placement. We have them for example, for Tikka T3, Sako 75-85, Remington and Sauer. Ask if what you want is not listed.
If you have a rifle with dovetail or weaver/picatinny base then a regular extdned base from Britannia, Hawke or BKL should do the job