Elasticity

You touch a creature.  The creature's form becomes rubbery and malleable. 

While you maintain concentration on this spell the target gains the following benefits:

• The target's speed increases by 10 feet until the spell ends.
• The reach of the target's melee attacks extends by 5 feet.
• The target has advantage to escape being grappled.
• The target has advantage on checks to grapple.
• The target can use a bonus action to increase or decrease in size by one category*.  (To a maximum of one category from its original size).
• The target's AC increases by 2.
• The target does not suffer the penalties associated with squeezing into smaller spaces.

*This change in size does not affect the target's carrying capacity.