Looks like the Extended gives 0.11 inches and the Extended Center Feed gives 0.3 inches extra magazine space. Is this true, are there more differences? Do they come with new followers and springs? Doug Extended - Precision stamped, stainless steel magazine box has .110" additional length to provide the required clearance for extra long rounds. Extended box and Long Window box have plenty of room for the popular .300 and .338 Ultra Mag and other calibers based on the .404 Jeffery case. Extra-long feed lips give reliable feeding with .284 Win. cases. Long and Short Window boxes have a triangular window that provides extra room for case shoulder; holds three rounds of these large diameter cases. Remington fits 700 ADL and BDL, requires minor modification to stock, receiver and bolt stop. WSM has a flat follower and center feed to prevent last round feeding problems with Winchester Short Magnum cartridges. M-70 fits Winchester Model 70; increases magazine length from 3.4" to 3.82". Requires machining receiver and altering bolt stop and ejector. SPECS: Stainless steel. Capacity: ADL - 3 rounds, BDL - 2 rounds. Extended - 3.91" (9.62cm) long. Long Window Box 3.91" long. Fits Remington 700 long action. Short Window Box 3.06" (7.6cm) long. Fits Remington 700 short action. WSM - Standard - 2.95" (7.5cm) long, fits 700 short action and Model 7. Extended - 3.06" (7.6cm) long, fits 700 short action. Capacity two rounds. M-70 3.82" (9.7cm) long, fits Winchester Model 70 long action. Capacity three rounds. EXTENDED CENTER FEED MAGAZINE BOX - Precision stamped, stainless steel magazine box feeds rounds from the center to correct feeding problems. .300" additional length provides the required clearance for extra long rounds. Extended box has plenty of room for the popular .300 and .338 Ultra Mag and other calibers based on the .404 Jeffery case. Fits 700 ADL and BDL, requires modification to stock, receiver and bottom metal. SPECS: ADL - 2 rounds, BDL - 2 rounds. Includes flatmetal follower.