The Maverick 88 pump-action shotgun has a magazine capacity of six to eight shells, depending on the model. This firearm comes with a factory installed "magazine capacity reduction plug." It's really no more than a wooden dowel with a rubber ring attached on each end, which keeps the owner from inserting more than two shells at a time. The two-shell limit conforms to hunting laws in many states where it is illegal to have a shotgun capacity greater than three (one in the chamber, two in the magazine). If your Maverick 88 does not have the plug, don't worry. It's easy to install.
Items you will need
1/4 inch diameter wooden dowel
2 rubber washers, internal diameter 1/4 inch
Loosen the take down screw assembly. Open the action on your shotgun halfway, then fully loosen the take down screw at the front of the magazine. This screw protrudes from the bottom of the barrel. It both caps the end of the magazine and connects the barrel to the magazine tube.
Remove the barrel. The entire shotgun barrel will slide forward easily, opening the end of the magazine tube.
Mount the rubber washers onto the dowel. The washers should be near each end of the rod. They are not essential, but they will keep your dowel from rattling around in the magazine tube. The length of your dowel rod depends on the length of your magazine tube, but it should leave at least six inches of space within the magazine to accommodate two 3-inch shells.
Place the dowel in the magazine tube. Slide the wooden dowel, with washers snuggly attached, into the open end of the tube.
Replace the barrel and tighten the take down screw. Carefully slide the barrel back into place. Firmly tighten the screw, sealing the magazine tube and attaching the barrel to the rest of the firearm.