The Thai grip fits my hand nicely, as I had hoped. I thought/hoped the Thai grip was closer in size to S&W target grips, and smaller than the original DW grip...judging by the checkered area and the amount of non-checkered area nearby, which is just a guess, so I got lucky.
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I did some measuring using a calipers, mostly for myself and future reference.
the first number is front to back at top of checkering
the second number is left to right at top of checkering
the third number is front to back at bottom of checkering
the last number is left to right at bottom of checkering
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S&W 1.630 - 1.325 - 2.210 - 1.500
DW 1.720 - 1.325 - 2.360 - 1.570
Thai 1.640 - 1.310 - 2.200 - 1.350
The bonus gift of foam ear plugs was interesting, and they are hard as concrete.