Chastity device: will it shrinks for ever?

[fsafe]

I'm thinking about using a chastity device 'cause i find them hot but mainly to help myself in stopping masturbation (or at least make it more difficult). But i'm worried about shrinking, i don't want to shrink my penis! I know it will happen eventually depending on the time i'll be locked, but is this effect for ever? Or it will recover its normal size once unlocked? 

Plus, i would thank you to give me some advice in chosing one (size, material, etc.) My size is 16,5 x 14cm when hard (6.5 x 5.5 inch) and 10 x 11cm when soft (3.9 x 4.3 inch)