[CAUT] key tops

[rwest1 at unl.edu]

Are all plastic key tops created equal?  I just had a set of keys  
recovered by my usual vendor and the plastic seems softer then usual,  
i.e., more easily damaged.  Some key tops seem to be practically  
indestructible.  How do I know what I'm getting?  Is there some  
standard that I can specify to be sure I'm getting a good quality  
material?

Richard West