If you use this PCC Buffer Weight/Spacer in a standard carbine buffer tube, it will add 2.5 oz and shorten the stroke by .75". 5" barrel guns don't run as hard as longer barreled PCCs so it's a matter of it your gun runs well with it or not. Also, short stroking the action is not always desirable. Short stroking increases recoil impulse, and you lose the use of your bolt catch. If you use this weight with an A5/AR10 carbine buffer tube, then you would have more weight but still have full stroke. This often feels softer. If you have a suppressor, this can also be desirable.
No, this weight is to be used with either the standard RB5007 buffer or the RB5015HD buffer.