M5 Neoprene Well Nut M5 with 20mm Stainless Steel Pozi Screw (Pack 6) (E)

What is the diameter of the well nut flange. What is the thickness of this flange. What is the over all length of the well nut

Will these work good for mounting handles on my kayak? Worried about them ripping off when I pick it up.

Can these be used to secure a sending unit in a plastic gas tank?

What is the screw size? 1/4 x 20 Standard Measurement?