Clack 990S head upper screen install?

I have a Clack 990s head. I need to install the top screen.
I tried to find a Clack D1225-05, but could find no one
selling it. I then ordered the D1203, which is a bayonet
type of locking type just like the D1225-05 screen, and is
a cheaper screen. I ordered 2 D1203 one light colored
the other a darker gray. For the life of me I can not install
ether one, both have too large top diameters.
I guess I have not gotten original Clack parts!!!!
Does anyone have any advice..I need to get this AN tank
installed Soon........Thanks jo

The 990s uses the common bayonet style, but Clack and Fleck are slightly different.

The WS-D1225-05 is the best top screen made. I sent you a PM

Thanks Dittohead...I did respond to Your email
Address.