A nice hop-up for a standard car - and a perfect replacement for top Tamiya 1/10 touring cars like TRF415/6 and TB Evo's in Tamiya Hop-Up blue.
Ball connectors are a consumable part, and you should always replace them when they start showing any signs of wear. You get 10 in this pack, and you will almost certainly not need all of them - for instance my TRF415MSXX takes 6-7, so I have got a few spare. If you buy 2 packs you would pretty much end up with at-least 3 full sets of replacement parts - and a very good price here too!
If you are replacing the ball connectors you really should buy Tamiya part no. 53601 - 5mm low friction adjusters. You get 8 of these in a pack, which would make up 4 tie-rods. These are HIGHLY recommended, they are very cheap and your old tie-rod connectors may be in poor condition - so it's worth replacing these too at the same time.