I changed my master cylinder reservoir on my 93 Vette, as I was bored and figured while the car is down doing water pump, suspension etc etc.
Well, when I took it off the unit only had two seals, ( I have had this since 96). So, I checked the FSM and it showed it only had two. Seems kinda strange as the reservoir from GM came with 2 seals, a large one and a little one. The little ones were the same as the ones that go into the master cylinder. Its not leaking, and wasn't leaking before, and it doesn't fit tight, just snug.
Is this normal? Most threads on replacing this people are using vices/blocks of wood, freezing the plastic reservoir prior to install etc etc.
Heres the old one as it came off.
[IMG]http://i33.photobucket.com/albums/d80/Steve40th/DSCF0028-1.jpg[/IMG]

I've never been able to pull one of those off without a ton of force.

But it's not under any pressure, so it shouldn't take much to keep it sealed.

I would hate that odd chance of it coming loose though during hard driving...

I was a little confused too. It came off easy, never had leaks ever. And when it came off it had just the two black seals. I tried to put the larger two that were with it, but there is no way for them to fit anywhere.
I put it on and pumped the brakes real hard, and no leaks. Its on firm, but you can move it left and right a little.
I need a picture from the side to see if the reservoir is flat up against the master cylinder, as mine has a little gap

on my 84 they were hard as L both ways ,,,very tight fit on new very hard n time consuming to git em stuck in new master,,,but now i have brakes

I read on another forum where someone with a93 had the same issue as mine, it came right off and went right back in with no drama. I swear, my 93 is weird, I have found so many 93 specific items, its mind boggling.