Center pad      Pin length      Pin width
SiLabs C8051F326 [10]   2.9/3.15/3.35   0.35/0.55/0.65  0.18/0.23/0.3
Atmel AT86RF231 [11]    3.2/3.3/3.4     0.3/0.4/0.5     0.18/0.23/0.3
Atmel ATmega32U2 [12]   3.5/3.6/3.7     0.3/0.4/0.5     0.18/0.25/0.3

[10] http://www.silabs.com/Support Documents/TechnicalDocs/C8051F326.pdf
[11] http://www.atmel.com/dyn/resources/prod_documents/doc8111.pdf
[12] http://www.atmel.com/dyn/resources/prod_documents/doc7799.pdf