<font color="aa00aa">hi dor,
u can refer to the following for reference, XS is just nice for 3yo, maybe S is big but not too big</font>
<table border=1><tr><td>Size</TD><TD>Alpha</TD><TD>Height in Inches</TD><TD>Weight in lbs</TD><TD>Age</TD><TD>Chest in Inches</TD><TD>Waist in Inches </TD></TR><TR><TD></TD><TD></TD><TD></TD><TD></TD><TD></TD><TD></TD><TD> </TD></TR><TR><TD>0-3m</TD><TD></TD><TD>up to 22"</TD><TD>up to 11 lbs</TD><TD>0-3 mos</TD><TD></TD><TD> </TD></TR><TR><TD>3-6m</TD><TD></TD><TD>22-25"</TD><TD>11-15 lbs</TD><TD>3-6 mos</TD><TD></TD><TD> </TD></TR><TR><TD>6-9m</TD><TD></TD><TD>25-27"</TD><TD>15-18 lbs</TD><TD>6-9 mos</TD><TD></TD><TD> </TD></TR><TR><TD>12m</TD><TD></TD><TD>27-29"</TD><TD>18-22 lbs</TD><TD>9-12 mos</TD><TD></TD><TD> </TD></TR><TR><TD>18m</TD><TD></TD><TD>29-31"</TD><TD>22-26 lbs</TD><TD>12-18 mos</TD><TD></TD><TD> </TD></TR><TR><TD>24m</TD><TD></TD><TD>31-33"</TD><TD>26-29 lbs</TD><TD>1-2 yrs</TD><TD></TD><TD> </TD></TR><TR><TD>2T</TD><TD></TD><TD>31-34"</TD><TD>26-29 lbs</TD><TD>1-2 yrs</TD><TD>20½"</TD><TD>20" </TD></TR><TR><TD>3T</TD><TD></TD><TD>34-38"</TD><TD>29-33 lbs</TD><TD>2-3 yrs</TD><TD>21"</TD><TD>20½" </TD></TR><TR><TD>4T</TD><TD></TD><TD>38-42"</TD><TD>33-37 lbs</TD><TD>3-4 yrs</TD><TD>22"</TD><TD>21" </TD></TR><TR><TD>5T</TD><TD></TD><TD>42-45"</TD><TD>37-53 lbs</TD><TD>4-5 yrs</TD><TD>23"</TD><TD>21½" </TD></TR><TR><TD>2</TD><TD>XXS</TD><TD>31-34"</TD><TD>26-29 lbs</TD><TD>1-2 yrs</TD><TD>20½"</TD><TD>20" </TD></TR><TR><TD>3</TD><TD>XXS</TD><TD>34-38"</TD><TD>29-33 lbs</TD><TD>2-3 yrs</TD><TD>21"</TD><TD>20½" </TD></TR><TR><TD>4</TD><TD>XS</TD><TD>38-42"</TD><TD>33-37 lbs</TD><TD>3-4 yrs</TD><TD>22"</TD><TD>21" </TD></TR><TR><TD>5</TD><TD>S</TD><TD>42-45"</TD><TD>37-43 lbs</TD><TD>4-5 yrs</TD><TD>23"</TD><TD>21½" </TD></TR><TR><TD>6</TD><TD>S</TD><TD>45-48"</TD><TD>43-50 lbs</TD><TD>5-6 yrs</TD><TD>24"</TD><TD>22" </TD></TR><TR><TD>7</TD><TD>M</TD><TD>48-51"</TD><TD>50-57 lbs</TD><TD>6-7 yrs</TD><TD>24¾"</TD><TD>22½" </TD></TR><TR><TD></td></tr></table>