diff --git a/src/swift_vel_part.h b/src/swift_vel_part.h
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index 0000000000000000000000000000000000000000..7d0a62a0b87cf1b48ebdb813f4e337a9e3564689
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+++ b/src/swift_vel_part.h
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+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Copyright (c) 2018 James Willis (james.s.willis@durham.ac.uk)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+#ifndef SWIFT_VELOCIRAPTOR_PART_H
+#define SWIFT_VELOCIRAPTOR_PART_H
+
+/* SWIFT/VELOCIraptor particle. */
+struct swift_vel_part {
+
+  /*! Particle ID. If negative, it is the negative offset of the #part with
+     which this gpart is linked. */
+  long long id;
+
+  /*! Particle position. */
+  double x[3];
+
+  /*! Particle velocity. */
+  float v[3];
+
+  /*! Particle mass. */
+  float mass;
+
+  /*! Gravitational potential */
+  float potential;
+
+  /*! Internal energy of gas particle */
+  float u;
+
+  /*! Type of the #gpart (DM, gas, star, ...) */
+  enum part_type type;
+
+} SWIFT_STRUCT_ALIGN;
+
+#endif /* SWIFT_VELOCIRAPTOR_PART_H */