You can use any kind of silicone I think, all of the ones I've been looking at can tolerate temps. of up to 220 degrees celcius - don't know how much that is in fahrenheit
Since the silicone is dry and rubbery when you punch the needle through there is no clogging, it cuts through!
I think something wen't a bit wrong in my medium preparation or maybe the seed were just not viable.. I've only got 6-7 protocorms in one of the jars Perhaps my temps. arent quite high enough, the jars are placed on my windowsill and they feel quite cold in the morning! However there has been no contamination in any of the jars so the sowing method works!
On a side note I'm working on a small project to construct a jar that contains two different media, one for germination and one for replating. I think I've come up with a method of actually replating in the jars, so you won't have to open the lid and risk contamination
I'll post pics once I get it done, but I haven't really started yet - it's all in my head for now