The K70 is front or rear,both are 4.00x18.I would of liked the K180 dirt track tyre,I have used these on gravel and seal before...the 120/90x18 was listed by my supplier,but not available.On dirt tracks in New Zealand we used speedway rear tyres in 19in,or competition trials tyres in 18in....I've used both.I'd still like to use trials tyres,but modern ones are too soft.The Michelin XII is good,but expensive.I'm very impressed with the K70's on gravel and hard pack,much,much better than I expected - also with the very soft compound they stick like slicks on seal.
I'll put some pics in higher resolution in the gallery.