Weber 40's slot in or bolt on trumpets?

[novathere]

What ones do I need? Came with bolt on but venturis move is this normal? Also can anyone confirm what ones these are?

[novathere]

[Royston]

Venturis slide in but there are held in place with a small clip in the slot, should only be a small amount of movement.

I see there are nylok nut retaining the trumpets, good idea, I have seen the damage a nut can do when drawn through into the engine!!