This standard size piston fits:
EG1000 A GENERATOR
EG1400Z A GENERATOR
F400K1 A2 ROTOTILLER
G150 HQAF ENGINE
G150 HZDU ENGINE
G150 PEAF ENGINE
G150 QAF ENGINE
G150 QZDU ENGINE
G150 UA5 ENGINE
GV150 A1 ENGINE
GV150 A2 ENGINE
GV150K1 A1D ENGINE
HR21 PDA LAWN MOWER
HR21 PXA LAWN MOWER
HR21 SDA LAWN MOWER
HR21 SXA LAWN MOWER
HR21K1 PDA LAWN MOWER
HR21K1 PXA LAWN MOWER
HR21K1 SDA LAWN MOWER
HR21K1 SXA LAWN MOWER
HR21K2 PDAM LAWN MOWER
HR21K2 SXA LAWN MOWER
HR21K2 SXAM LAWN MOWER
HRA21 SDA LAWN MOWER
HRA21 SDAW LAWN MOWER
HS35 A SNOW BLOWER
WA20K1 C WATER PUMP
WA20K1 D WATER PUMP
WB20T DRA WATER PUMP
Not in original packaging
If there's even a chance you'll need this/these replacement part(s) in the future you'd better get them NOW!. Keep this in mind, replacement parts are always good to have. When you decide to sell your Honda, including a few extra replacement parts always sweetens the deal for both buyer and seller.