What size filter for HCG amp?

What size filter should i use for a hcg amp?

I have never used a filter. Am I missing something?

I just use the water given with the amp mix it then shoot.

No need to filter, you reconstitute it with sterile BW.

Im not sure what the filter could be used for. Its all sterile you shouldnt need anything else but a syringe.

broken glass from the amp.