I need a spinner nut for one of my planes but I do not understand the measurements given by tower hobbies

for example

SPECS Shaft Size: 1/4-28
Weight: 4oz
Diameter: 1"
Length: 1.5"

( http://www2.towerhobbies.com/cgi-bin...8&I=LXL715&P=K )

what is 1/4-28 in metric and is this both the shaft diameter and lenght?


also


SPECS Shaft Size: 8x1.25mm
Weight: 2oz
Diameter: 7/8"

( http://www2.towerhobbies.com/cgi-bin...8&I=LXL736&P=K )

I'm guessing that the eight is the diameter but what does 1.25mm describe?



The engine I need this for has a 6.2mm diameter and without the prop and all it´s 32.8
in length, what would that be in that system?

(also I know the links to those nuts isn´t maby what fits the engine but they are examples)