Today I acquired...........

[The_Yellow_Ardvark]

Sadly most foam ones are not frost proof.

Yes they are.

 

[Memmeddu]

I kept all the reducer rings for blades they have saved my bacon sever al times

Unfortunately I don't have any others because it's my first cutoff ever and I didn't collected any.
I've removed the 30mm washer, and used a 2.5mm electrode bent to make a ring and used that, then the disc plate have a recess wich allowed me to use the centering washer to prevent the electrode right to slip off the blade.
It worked out fairly well as a temporary solution but I have to seek for a proper reducing ring.