Find: Indexing for immediate use

In the Find documentation I found that, for testing purposes, you can do:

client.Index(toIndex, x => x.Refresh = true);

However, when toIndex is a list of objects, I get the following error:

{"Invalid type id. Maximum 200  word characters (letter, number, underscore, dot, comma): System_Collections_Generic_List`1[[DGTNext_Api_Data_DB_Product, DGTNext_Api_Entities, Version=1_0_0_0, Culture=neutral, PublicKeyToken=null]]."}

Iterating causes no error:

foreach (var prod in toIndex) client.Index(prod, x => x.Refresh = true);

It is a short list, 5 small objects. Still, it seems it's over some (quite small) limit for immediate indexing, is that correct?

So, my next question is, if I have to do the iteration, do I need to add the Refresh = true clause for each object, or is it sufficient to do it for the last one? In other words, does the Refresh just mean "process this object" or "process all unprocessed objects"?

Thanks.