A bumper is any one of several periodic color-preserving glider reflectors, most of which were discovered by Tanner Jacobi on 6 April 2016. The theoretical lowest repeat time is 34 ticks, but this can not be achieved in practice by currently known bumper variants.
At gen 11 or 12, a spark is needed. A dot spark can be used on gen 11 (such as from the blocker). The spark from the grin (such as from the Coe's p8) at gen 12 can also work; at gen 20, a glider an R-pentomino is produced. The glider escapes, and the R is converted back to a loaf using an eater 1.
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RLE: here Plaintext: here
A p2 bumper, if discovered, would provide non-trivial oscillators for periods 34 and 38 which are currently unknown as of January 2019, and a stable one would presumably allow for a period 41 oscillator.