Well, my kit bag contains...
1x Race suit
1x Helmet
1x Boots
1x Gloves
1x Back protector
1x Jonny Suit
1x Under suit
2x Rash vests
4x Tees
2x Towels
1x Transponder
3x Visors
4x Undercrackers
5x Pairs socks
2x Hoodies
1x Jeans
2x Shorts (optimistic)
...and I still had room for more stuff - I just don't have more stuff
It's a big Alpinestars kit bag, and I can't imagine many bags that would be bigger. You'd struggle to lift them.
So don't worry about the size of your sack too much