When you earn the amount of points listed with the kit indicated in multiplayer mode then you will unlock the item shown.

Assault Kit

4,000 points: Defibrillator
11,000 points: M320
22,000 points: M416
38,000 points: M26 MASS
60,000 points: AEK-971
89,000 points: M16A3
124,000 points: F2000
166,000 points: AN-94
220,000 points: M16A4 (RU) and AK-74M (US)

Engineer Kit

3,000 points: FIM-92 Stinger (US)
3,000 points: SA-18 IGLA (RU)
7,000 points: M15 AT Mine
14,000 points: SCAR-H
25,000 points: EOD Bot
40,000 points: M4
58,000 points: A-91
82,000 points: FGM-148 Javelin
110,000 points: G36C
145,000 points: M4A1 (RU) and AKS-74u (US)

Support Kit

4,000 points: C4 Explosives
11,000 points: M249
23,000 points: M18 Claymore Mine
40,000 points: M224 Mortar
60,000 points: PKP Pecheneg
90,000 points: M240B
130,000 points: M60E4
170,000 points: M2 IAR (RU) and RPK-74M (US)

Recon Kit

5,000 points: T-UGS
13,000 points: SV98
26,000 points: SOFLAM
45,000 points: MAV
71,000 points: SKS
104,000 points: M40A5
146,000 points: M98B
195,000 points: MK11 MOD 0 (RU) and SVD (US)