From what information I could find the HERA Arms CQR AR-15 Stock System CA Compliant model "compliance plate cover" is non removable.
The HERA Arms CQR AR-15 Stock System is different than the AR10 model. The AR10 models are designed to match up to the DPMS Gen 1 receiver. Please email us at techsales@opticsplanet.com.
There are not different sizes of the HERA Arms CQR AR-15 Stock System. Please email us at techsales@opticsplanet.com so we can get more information about the problem you are having with the HERA Arms CQR AR-15 Stock System.
The HERA Arms CQR AR-15 Stock System California Compliant model has a plate inserted in the stock to prevent the use of the pistol grip. The regular model does not have this plate so the user can completely grab the pistol grip.
The HERA Arms CQR AR-15 Stock System works with Mil-Spec AR15's using carbine buffer tubes. The HERA Arms CQR AR-15 Stock System might work with the Smith and Wesson M&P15-22 but fitment cannot be guaranteed.
This will fit on an AR-10 if using a mil-spec carbine buffer.
The included QD cups must be installed into the stock before they will be able to accept a QD sling attachment. If the swivels are installed they may be out of spec. You can contact Hera Arms for replacement parts at the bottom of their product page https://www.hera-usa.com/kopie-von-h3-2.
It will fit if your AR-9 has a carbine length mil-spec buffer tube. It will not fir the Matrix AR-9 pistols with the pistol tubes. Please consult any state, local, and federal laws if considering using this product with an AR-9 pistol.
The HERA Arms CQR AR-15 Stock System does not include a buffer tube, spring, or buffer. It is designed to fit Milspec carbine length receiver extensions.
If you have an DPMS Pattern AR10 with a Mil-Spec Carbine Length buffer tube you will need the model at the link below.
https://www.opticsplanet.com/hera-arms-cqr-ar10-buttstock.html