sorry it only fits the 835 ulti mag 3.5 inch gun

Westley, no Sir, this Mossberg Replacement Barrel is compatible with Mossberg 835 Ulti-Mag 12 gauge models. The Mossberg 88 is cross compatible with Mossberg 500 parts. Cheers and stay safe!

Maverick 88 pump-action models are fully-interchangeable with Mossberg 500 barrels (within gauge and capacity). The diverse selection of available accessory barrels allow shooters to adapt their Maverick 88 for multiple hunting or security purposes.
Compatible 500 barrels here
mossberg.com/store/parts/model/maverick.html?product_list_order=price&product_list_dir=desc

No, this'll fit a mossberg 835 only