I wrote about this over the summer when I changed the battery on my 2002 RX300. I claim that you need a couple of washers as spacers on the front hold-down screw. Somebody else said they didn't and it fit perfectly. Perhaps they had a 1999-2000 model or something.

Anyway, I got a snug (but not too tight) clamping action with about maybe 3/16" worth of washers as spacers.