BlockSingle and BlockDual is made to replace original expensive ones. They will both fit straight and all curved tracks down to also R1. One BlockDual will replace two original ones and with this version the fence will come close to each other. Possible to be fitted with kerbs and/or fence and/or posts. BlockParallel is made to be able to keep two separate track lines attached to each other in a fixed distance. Possible to add kerbs on both sides as well as two types of fence(s). The round hole will fit ø6mm pipe directly (cheap ones from ebay) and original posts using a small file.