Hi Josh,
Thanks for your inquiry.
Yep, the RedEye Filter M67 (#5172) features a thread on both sides, therefore allowing for the BigEye Lens M67 (#5137) to be mounted on top of it, so you can use both the filter and the BigEye together.
You can also mount the SharpEye Macro Lens M67 (#5128) on top of the same filter, so you can take macro shots and videos with the filter as well.
Also, you might take into consideration that the EyeGrabber Lens Holder F67 (#4088) enables to secure any of these lens accessories once they are removed from the housing lens port. It attaches to any standard Flex or Ball & Joint arm and capable of holding any of our 67mm threaded lens accessories. This is especially useful with the BigEye Lens, which is too large to fit a standard BCD pocket and can get scratched or damaged if not properly secured.
Let me know if there's anything else I can help with!
Dive Safely,
Sharon