RE: converting a stihl
here are some of them off the top of my head .
Ryob
long shaft 3/8x24
short shaft 5/16x24
Homie
long shaft 3/8x24
short shaft 5/16x24
Poulan
36cc 3/8x24
54cc 3/8x24
42/46cc 5/16x24
60 cc 3/8x24
stihl
24.5 cc 8mmx1.00
27cc 8mmx1.00
or 3/8 x 24 if the long shaft
Husky
most smaller are 8mmx 1.00
thats all i can think of at this time .I may have to go to the shop and do some measuring on different ones