Beiter Plunger questions

[Focal]

Hey guys, just a quick question. I am upgradng to the Beiter plunger, and I am not sure about the thread in my riser. It is a Win&Win Exfeel, so I am not sure if it is the M4 thread or 5/16" thread. Also, if I am using the beiter rest, would you suggest the short version over the long version? I did try a search, but it has been a while since I have been to the forum, and the search feature doesn't seem to work very well, as in I can't find threads and posts I know I made by the search function, so there may be threads on this, but I couldn't find them. Thanks for the help.

[Progen]

Definitely 5/16 thread.

Actually, there is no short or long version because if your local dealer is not the lazy kind and too eager to take your hard earned cash, he'd inform you that there's actually 8 different lengths you can choose from.

17.5mm to 21.5mm
17.5mm to 23.0mm
21.5mm to 24.5mm
21.5mm to 27.0mm
23.5mm to 26.5mm
25.5mm to 29.5mm
29.9mm to 32.5mm
31.5mm to 34.5mm

Measured from the plunger tip to the end of travel for the locking nut.

On the other hand, if YOU're too lazy to wait or bother measuring, then simply take one of those with a longer body. Gives you more allowance to play around.