Hi Bruno
For a 2410;
The 3 screws ( machine bolts ) for the diaphragm are #6-32 by 3/4" long ( or @ 19 mm long )
The 2 screws ( machine bolts ) for the back-cap are #8-32 by 1.5" long ( or @38 mm long )
For a 2420/1; Don't have one to measure
For a 2426;
The 3 screws ( machine bolts ) for the diaphragm are #6-32 by 3/4" long ( or @ 19 mm long )
The 3 screws ( machine bolts ) for the back-cap are #8-32 by .5" long ( or @ 13 mm long )
The bolts that hold in the diaphragm should be nonmagnetic ( brass ) - if you can find them .
regards <> Earl K