Raff's Op. 166, a pair of piano pieces, likely includes a spirited and technically demanding work characteristic of his prolific output.
Focus on developing finger dexterity and control in rapid octave passages.
2 Piano Pieces (Op.166) is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 6.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of 2 Piano Pieces (Op.166) lasts about 4 minutes.
2 Piano Pieces (Op.166) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.