The guiderail adapter is specific per model. You should just get the makita part specified for your router (and that adapter will also work on festool rails).
/edit I can't locate the part on the www.makitauk.com site, But according to the Dutch makita site it's partnumber 194579-2 if your router is one of the following: RP1110C, RP1800FX, RP2300FCX, RT0700CX3J, RP0900K, RP0910
/edit 2: Welcome to the forum [big grin]