Correct screw size for plugs in breezeblock wall

[SteUK]

Hi all,

Wonder if someone can offer some advice.

I am going to be fixing some cement backer boards to my bathroom walls with adhesive and a mechanical fixing. The wall is 3mm finish plaster, 10mm binding plaster, 50mm cinder/breezeblock. I am planning on using Fischer universal ux8 x 40mm plugs. Fischer state screw diameters of 4.5 to 6mm for this plug. Should I opt for 5mm or 6mm diameter screws?

Thanks!

 

[PrenticeBoyofDerry]

6mm non-corrosive

 

[Blagard]

I think the screw should be 6 gauge rather that 6mm. I not that certain the gauge and mm are the same!