What is the biggest dildo both length and girth one can use for anal fun without causing damage ?
Hi and welcome
take a look at the forum rules here
http://www.lovehoney.co.uk/help/forum-rules/
As to your question everyone has different limits but even the smallest toy can do damage if you are not careful
lots of advice on here
http://www.lovehoney.co.uk/community/forums/sex-toys/362-anal-sex-for-beginners-any-advice/
if you give more info someone will be able to give you a more specific answer but general advice is start smal, relax, take it slowly and lube. lots and lots of lube .
xGGx
Don't use anything bigger than your sphincters will stretch obviously, and be prepared to meet heavy resistance at the 7-12 inch mark as your colon angles sharply.
Everyone is different.