This is a DBM for Weatherby MkV Long Action rifles. Uses 300 WM or 338 Lapua AICS mags,(3.715 outside Dimension of Magazine) allows fast reloads and higher capacity. Install is required, and we can provide inletting and install services as well. Installs are free at CDiPrecision, so click Install option and send your rifle in for install. Easy and fast. 3 week turnaround or faster. US Addresses only. Mags Must be purchased Separately.