It came with the 10 stop glass filter and seems to be pretty great quality. I'm loving using it. Even ordered a 6 stop to go with it. 

First, K&F Concept ND2-ND400 lens filter allows changing shutter speed based on the effect you want with the best sensibility and the same aperture. Second, K&F Concept ND2-ND400 lens filter allows creating a blurred background with a large aperture while the shutter speed remains the same. Third, K&F Concept ND2-ND400 lens filter is designed to prevent overexposure and maintain image purity and quality at the same time. *Like a zoom lens, the variable nd filters are suitable for multiple shooting situations. If you're looking for perfect image quality, a fixed ND filter is recommended. 

The camea can take 1.6v rechargeable batteries, but in general rechargeable battery might drop its voltage quick depend on its physical performance. In the cold weather, recommend using Energize lithium batteries to get longer lifetime. 

This one is high quality materials, and contains both a variable ND filter + a polarizing filter. Also - most variable Nd filters show and “x” pattern when they’re turned to the max, essentially making them useless at full power. This one shows no “x” pattern. I’m happy I bought it! Very high quality and sturdy. 

Unlike a tube it won't effect your focus distance nor effect your quality like a doubler. The lens will have more of an effect than anything else. On my Sony a7, I must be sure to use a full frame lens since the sensor is 35mm size