This is a brand new 164cc bore up kit manufactured by Kitaco company in Osaka, Japan.
Complete set that includes all cylinder parts.
It is designed for genuine cylinder head and can be mounted on Honda MSX125 Grom, Monkey 125, Supercub C125 and CT125 Hunter Cub.
Please check your own vehicle features for compatibility.
Here are several additional informations from manufacturer:

Product description
BIG BORE KIT FOR STOCK CYLINDER HEAD. POWER / TORQUE INCREASES AGGRESSIVELY IN THE MIDDLE SPEED.
※I-MAP / BIG CAPACITY INJECTOR / HIGH CAMSHAFT (SOLD SEPARATELY) REQUIRED

Notes
â—‹ALUMINUM CYLINDER
○DISPLACEMENT:164cc
BORE O.D.:φ60
STROKE:57.9mm(STOCK)
○COMPRESSION RATIO:11.1:1
â—‹NON-LEAD PREMIUM GASOLINE TYPE

Applicable model

GROM

JC61

JC75

MONKEY125

JB02

SUPER CUB C125

JA48

CT125 HUNTER CUB

JA55