Implant i.e. injectable by subcutaneous or intradermal way in the form of a monophasic hydrogel, comprises hyaluronic acid (0.5-5 wt.%, preferably 2 wt.%), in which 50-95 wt.%, preferably 85 wt.% of hyaluronic acid is present in the form of cross linked gel, 5-50 wt.%, preferably 15 wt.% of the hyaluronic acid is present in the free form or in the form of one of its salts, a molecular mass is 500-2800 kDa, preferably 1000-1500 kDa, and the ratio of the cross linked hyaluronic acid gel weight and free hyaluronic acid weight is 1:1 to 1:0.5, in a carrier fluid. An independent claimS are included for: (1) a kit in the form of syringe comprising the injectable implant; and (2) a preparation of the injectable implant comprising introducing the hyaluronic acid in an isosmolar fluid and basic buffer fluid; inflating, cross linking and homogenizing by heat under slow agitation; neutralizing the obtained gel and eliminating the cross-linking agent; adding hydrated hyaluronic acid by a basic buffer solution; homogenizing the mixture; optional degassing; conditioning in flacons or syringes; and sterilizing. ACTIVITY : Dermatological. MECHANISM OF ACTION : None given. No biological data given.