Almost all Grasshopper cutting decks can have a mulch kit fitted. Mulch kits can range from a full deck modification with baffles and specialist mulch blades to just a plug that blocks the mouth of the deck.
Mulching keeps your lawn healthy and stimulates growth outside the growing season. However the grass needs to be cut higher leaving somewhere to hide the clippings. It works best in dry conditions with only 1/3 of the grass being cut. It can be challenging to get a nice finish when cutting wet grass or more than a third of the grass height.
See the pages below the video for more information on mulching and best practice when using a mulch kit.
To see the of finish a good operator can achieve with side discharge check out this video of a Grasshopper agent in Finland dealing with the Autumn leaves.