1/4-20 Threaded Insert Wood Insert Nuts Furniture Screw in Nut kit 151 pieces. 44 pieces 1/4 in. - 20 tpi x 20 mm threaded inserts + 44 pieces 1/4 in. - 20 tpi x 15 mm threaded inserts + 62 pieces 1/4 in. - 20 tpi x 10 mm threaded inserts + 1 piece 6mm hex key. Threaded insert head diameter: 0.461 / 11.7mm, body diameter: 0.315 / 8mm, threads diameter of 1/4-20 x 20mm / 15mm: 0.410 / 10.4mm, threads diameter of 1/4-20 x 10mm: 0.389 / 9.9mm. 1/4-20 Insert nut goes into a predrilled hole in wood and has internal threads, the Screw-In insert offers a strong permanent thread for wood. Threaded insert features durable construction for a long-lasting hold, ideal to use in furniture applications.