Ditto to all the above. I am using one on my P25/RB600 combo, as well as my OL/P3 combo. Have not changed the one on my P9/RB900, yet, because I want to upgrade to an RB1000, when I can.
I would not have believed that eliminating the stock weight could actually make that much difference.
It is a relatively inexpensive upgrade, and well worth the money. Go for it!